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A FEW OPINIONS. 


“The processes of assaying are detailed with great clearness ''—Popular 
Science Monthly, July, 1883. 

“ It is just such a book as is needed to assist those who are, by actual work, 
developing the gold and silver mines of the country.”— Chicago Tribune, 
March 31, 1883. 

“The author has faithfully endeavored to carryout his idea of a plain, 
practical work. No one will be a loser who possesses it.”— Mining and Scien¬ 
tific Press, San Francisco, A ug. 18, 1883. 

“Has endeavored, we may add, with marked success, to prepare a work 
on assaying ”— Engineering and Mining Journal, April 28, 1883. 

“ The book will form an excellent elementary guide to the important art of 
assaying.”— Chemical News, London, June 8, 1883. 

“ Mr. Brown has succeeded in providing a valuable assistant for the stu¬ 
dent, the miner, and the assayer.”— Mining Review, March 29, 1883. 

“ This handy volume appears to contain sufficient information in the art of 
assaying to entitle it to the claim of being a manual of instruction to begin¬ 
ners.”— Scientific American, July 14, 1883. 

“ There is probably no other book in the English language that so fully 
meets the wants of those for whom it was made as this manual.”— Journal 0/ 
Education, Boston, Sept. 25, 1884. 

“ It is a complete compendium of everything pertaining to the assaying of 
the above-mentioned ores.”— Mining Record, April 7, 1883. 

“ Fort Maginnis, Montana, July 22, 1885. 

“Allow me, as a miner, to thank you for your manual. It is written in 
English, and for * us,’ and not for Freiberg men.”— Eugene Smith. 

“ Portland, Ore., March 15, 1886. 

“ My opinion is, that for clearness, accuracy, and adaptation to the uses of 
an American assayer, it is worth all the other assay books that I am acquainted 
with.”—H. O. Lang. 

“ Lawrence, Kas., July 22, 1884. 

“ Your book is plain and to the point, and just the thing for beginners.”— 
E. W. Walter. 

“ San Francisco, Cal., Aug. 30, 1886. 

“ I congratulate you upon this little book. I wish other writers on metallur¬ 
gical subjects would write in as plain English.”—Louis Janin, Mining Engi¬ 
neer. 

“ Chicago, April 3, 1883. 

“ The most essential point that struck me was the plain, common-sense man¬ 
ner in which you handle the subject. If more of our scientists would follow 
where you have dared to lead, and would free their subjects from useless tech¬ 
nicalities and abstruse phrases, there would be less stumbling and misunder¬ 
standing among their students and readers, and more confidence given to them 
by those who have need of their services.”—H. D. Whittemoke, C.E. and M.E. 





















































manual of assaying 


Gold Silver Copper 

AND 

LEAD ORES 


WITH ONE COLORED PLATE AND ONE HUNDRED AND 
THIRTY-TWO ILLUSTRATIONS ON WOOD. 


BY 

WALTER LEE BROWN B Sc 


FOURTH EDITION 
(fourth thousand) 



CHICAGO 

PUBLISHED BY E LI SARGENT & CO 

1S92 







i NS so 


Copyright, 

By WALTER LEE BROWN, 
A. D. 1886 . 


Copyright, 

By WALTER LEE BROWN, 
A. D. 1892 . 



THE LAKESIDE PRESS. 

R. R. Donnelley & Sons Company, Printers, 






CHICAGO. 


EXTRACT FROM PREFACE TO FIRST EDITION. 


When I entered upon the task of preparing this 
book, it was with the idea of furnishing a guide to 
those, who, having had no previous technical or es¬ 
pecially scientific education, desired to learn some¬ 
thing of the practical assaying of gold and silver ores , 
and in whose hands I could place no work that could 
give them this information in a clear, simple and thor¬ 
oughly detailed manner, and unburdened with un¬ 
necessary matter. 

This intention I have tried to adhere to all the way 
through, and while I have added other information 
which was pertinent, I have kept such increase in an 
appendix, so that the body proper of the work con¬ 
tains the real subject matter. 

It is my sincere belief that there is no book in the 
English language on the subject of assaying which 
occupies the space that this little manual tries to fill. 

A number of such publications fail to meet the 
want, on account of their antiquity, they having been 
written some thirty years ago ; hence their methods, 
apparatus, etc., are not suited to the assayers of to¬ 
day. Others are either more suitable as books of 
reference, or do not give sufficient detail for the inex¬ 
perienced. 

It is this latter fault I have carefully endeavored 
to avoid, and perhaps have gone to the other extreme. 
At all events, I have tried to give here in print the 



6 


PREFACE. 


precise instruction which I have previously imparted 
orally to my students. Those who may choose to 
criticise, will remember for whom this hand-book is 
written. 

I wish to publicly thank the following gentlemen 
who have very kindly aided me in my work with 
valuable information: Mr. S. A. Reed, Irwin, Colo.; 
Mr. A. II. Low, Assayer of the Boston and Colorado 
Smelting Works, Argo, Colo.; Mr. C. Boyer, Assayer 
of the U. S. Branch Mint, Denver Colo.; Mr. M. G. 
Nixon, Engineer, and Mr. R. G. Coates, both of 
Chicago. 

March, 18S3. 


PREFACE TO THE SECOND EDITION. 

So many words of praise, both from the press and private 
individuals, greeted the first edition of this work, that I feel 
encouraged to put forth a second and greatly improved edition, 
which will not contain the faults that have been pointed out 
to me as existing in the first. 

The salient features of the new comer are increase in mat¬ 
ter from 318 to 488 pages; the stating of all charges in assay 
tons, grammes, and grains; detailed charges in the scorification 
process; full notes on the colors and appearances of the scori- 
fiers (with a colored plate) and cupels after work; the expan¬ 
sion of the crucible process from nine to almost ninety pages; 
more complete articles on the assay of gold and silver bullion, 
and the volumetric analysis of copper ores; and, finally, the 
issuance of the book in flexible covers. 

For the idea of the oxidizing powers of ores which I have 
developed in the notes on the crucible process, I am indebted 
to Aaron’s Assaving. 

Whatever appears in this edition extracted from the follow- 






PREFACE. 


7 


ing authorities, is given with the full and written permission of 
the authors , editors , or owners of the copyright , as the case may 
be: Mitchell’s Manual of Assaying, Kustel’s Roasting: of Gold 
and Silver Ores, Aaron’s Assaying, Chapman’s Furnace Assay, 
and Hank’s Fourth Annual Report as the State Mineralogist 
of California. 

Besides for that which I have incorporated from the above- 
mentioned sources, I wish to give thanks to the following gen¬ 
tlemen: to Mr. J. C. Jackson, my successor in business in Chi¬ 
cago, for illustrations of a permanent furnace, and particu¬ 
larly for the neat and characteristic frontispiece; to Mr. F. E. 
Fielding, Assayer, Virginia City, New, for valuable notes on 
the assay of gold bullion and volumetric analysis of copper 
ores; and to Mr. G. H. Ellis, for the careful working out of the 
qualitative schemes. 

October i, 1886. 


NOTES TO THE THIRD EDITION. 

This edition differs from the previous one only in the cor¬ 
rection of a few typographical errors; in the revision (and re¬ 
duction) of the prices of a number of articles listed in the 
assayer’s outfit on pages 439-441, and some minor alterations 
in the descriptions of apparatus and re-agents. 

It has been a matter of gratification to both publisher and 
author that at least one-fourth of the second edition has been 
sold in England, Germany and Australasia, and this without 
making any special effort to effect its sale in foreign countries. 

July, 1889. 


NOTES TO THE FOURTH EDITION. 

In the course of time, all books, and especially tech¬ 
nical works, become more or less obsolete, unless they 
keep pace with the improvements and progress of the age. 
So with this little work, it must be fully up to the 





8 


PREFACE . 


times, consequently the section on apparatus has been 
thoroughly revised, all matter, both illustrative and 
descriptive, representing apparatus not now commonly 
used, has been expunged, and new forms have been 
added. We have also reason to believe that the illus¬ 
trations to this work have been considered as among its 
most important features, so that their number has been 
increased from ninety-four to one hundred and thirty- 
two. 

Amongst the methods, some of those on “ Lead 
Ores” have been re-written in accordance with the re¬ 
sults of recent investigations. In the appendix, chap¬ 
ters have been added on the “ Tin Assay,” on “ Gold 
and Silver Ores and Minerals,” and a short chapter on 
the u Determination of the Specific Gravity of Min¬ 
erals.” 

To fit the manual for the English market, where 
many copies of the previous editions have found a 
welcome, the pecuniary values of apparatus, etc., 
which have heretofore been given only in American 
dollars and cents, will now be found additionally in 
their English equivalents. 

There has in general been a sharp revision, mak¬ 
ing good many little omissions, adding clearer ex¬ 
planations, and so on, all tending to bring this book a 
little nearer to that plane of perfection which we all 
seek. 

January, 1892. 


Walter Lee Brown. 



CONTENTS 


PART I. 

APPARATUS AND RE-AGENTS. 

CHAPTER I. 

APPARATUS USED IN ASSAYING. 

Implements for Pulverizing, Sampling, etc., - - 20 

Scales and Balances,.42 

Weights, - 65 

Furnaces, - -.70 

Furnace Tools,.98 

Apparatus Used in the Furnace, ... io 8 

Apparatus of Glass and Porcelain, - - - 118 

Miscellaneous Apparatus,.124 

CHAPTER II. 

RE AGENTS USED IN ASSAYING. 

Dry Re-agents for Assaying,.141 

Wet Re-agents for Assaying, - - - - 155 

Re-agents for Analysis, - - - - - 158 

Miscellaneous, .... ... 166 

CHAPTER III. 

TESTING OF RE-AGENTS. 

I. Testing of Litharge for Silver, - - - 168 

II. Testing of Granulated Lead for Silver, - 172 

III. Testing of Sheet Lead for Silver,- - - 174 

IV. Determination of the Reducing Powers of 

Reducing Agents,.175 

V. Determination of the Oxidizing Power of 

Nitre (Nitrate of Potash), - 176 

9 






IO 


CONTENTS. 


PART II. 

ASSAYING. 

CHAPTER I. 

GOLD AND SILVER ORES. 


Occurrence,. 181 

Assay,.184 

I. Preparation of the Sample, ... 185 

II. SCORIFICATION PROCESS, .... 195 


a. Preparation of Charge, 197; b. Scorifica- 
tion,2o8;r. Cupellation, 214; if. Weighing 
the Gold and Silver Bead, 223; e. Parting, 

224; f. Inquartation, 228; g. Weighing 
the Gold Residue, 229; h. Calculations, 230. 

III. Crucible Process, .231 

Preliminary, 231; Roasting, 273; Methods 
of the Crucible Assay, 278; Preparation of 
the Charge, 281; Running the Crucibles 
in the Fire, 287; General Charges, 290; 


Special Charges and Directions, 296. 
CHAPTER II. 

COPPER ORES. 

Occurrence, .318 

Assay,. 319 

I. Method for Native Copper, - - - 320 

II. Method for Oxides and Carbonates of 

Copper, 321 


III. Methods for Sulphides of Copper, - 321 


CHAPTER III. 

LEAD ORES. 

Occurrence,. 3215 

Assay,. 326 

I. Methods for Galena,. 326 


II. Methods for Oxides and Carbonates, 






CONTENTS. 


I I 

APPENDIX. 

SECTION I. 

Special Methods. 

I. Assaying of the Various Minerals Con¬ 
tained in an Ore,.341 

II. Assaying of Ores Containing Free Gold 

or Free Silver, -.34.3 

III. Analysis of Copper Ores, - 347 

IV. Amalgamation Assay or Laboratory Mill 

Run,. 365 

V. Pan Test for Gold (“ Panning ” ), - - - 369 

VI. Chlorination Assay of Gold Ores, - - 378 

VII. Chlorination Test for Silver, - - - 381 

VIII. The Assay of Gold and Silver Bullion, - 383 

IX. The Assay of Base Bullion, - 418 

X. Qualitative Tests; Carbonates, Sulphates, 
Sulphides, Tellurides, Copper, Iron, Lead, 

Manganese, Silver,.422 

XI. Brief Scheme For Silica, Iron, and Manga¬ 
nese, .427 

XII. Determination of Moisture in an Ore, - 429 

XIII. Determination of Sulphur in Pyrites, - 430 

XIV. The Assay of Tin Ores, .... 43! 

XV. Gold and Silver Ores and Minerals, - - 434 

XVI. Determination of Specific Gravity of Min¬ 
erals, 459 

SECTION II. 

Lists and References. 

List of the Principal Gold Minerals Found in 

the United States, -.461 

Minerals Likely to Carry Gold, - - - - 462 

List of the Principal Silver Minerals Found in 

the United States, ...... 462 





I 2 


CONTENTS. 


Minerals Likely to Carry Silver, - 465 

List of the Principal Copper Minerals Found in 

the United States,.466 

List of the Principal Lead Minerals Found in 

the United States,.469 

List of Useful Books on Subjects More or Less 
Connected with Assaying: General Science; 
General Chemistry;Chemical Technology; Ref¬ 
erence Books on Chemistry; Text-Books on 
Theoretical Chemistry; General Qualitative 
Analysis; General Quantitative Analysis; 
Special Quantitative Analysis; Volumetric An¬ 
alysis; Laboratory Manipulation; Geology; 
Mineralogy; Blow-pipe Analysis; Metallurgy 
and Mining; Assaying; Metric System—Weights 


and Measures; Mining Law,.472 

Plan for Assay Laboratory,.481 

Form for Certificate of Assay, .... 482 

Outfit, Assaying,.483 

Outfit, Blow-pipe,.48^, 


SECTION III. 

Tables. 


Multiplication Table for Gold and Silver, - - 487 

Table of Values of Gold and Silver, - - 488 

Tables of Weights: Avoirdupois; Troy; Apothe¬ 
caries’; French or Metric System, - 489 

Equivalents of Some of the English and French 

Weights,. 493 


Assay Ton Equivalents in Grammes, Troy Grains 
and Troy Ounces,. 


Index, 


505 






INTRODUCTION. 


In our present state of knowledge we be¬ 
lieve all matter to be composed of one or 
more elements or original simple substances. 

These elements are considered to be sev¬ 
enty in number. Certain of them have what 
we may call a commercial importance. (See 
Introduction to Attwood’s Blow-pipe Assay¬ 
ing.) They are as follows, the metals being 
in italics: 


I. 

Aluminium. 

16. 

Gold. 

2. 

Antimony. 

i 7 - 

Hydrogen. 

3 - 

Arsenic. 

18. 

Iodine. 

4 - 

Barium. 

19. 

Iridium. 

5 - 

Bismuth. 

20. 

Iron. 

6. 

Boron. 

21. 

Lead. 

i 

7 

Bromine. 

22. 

Lithium. 

8. 

Cadmium. 

23- 

Magnesium. 

9 - 

Calcium. 

24. 

Manganese. 

IO. 

Carbon. 

2 5 - 

Mercury. 

11. 

Chlorine. 

26. 

Molybdenum. 

12. 

Chromium. 

27. 

Nickel. 

13 - 

Cobalt. 

28. 

Nitrogen. 

14. 

Copper. 

29. 

Oxygen. 


Fluorine. 

3 °* 

Palladium. 



IN TROD UC TION. 


H 


31. Phosphorus. 

32. Platinum. 

33. Potassium. 

34. Silicon. 

35. Silver. 

36. Sodium. 

37. Strontium. 

38. Sulphur. 


39. Tin. 

40. Titanium. 

41. Tungsten. 

42. Uranium. 

43. Vanadium. 

44. Zinc. 

45. Zirconium. 


Some of the above are valuable in them¬ 
selves, others in combination. 

The remainder of the elements, which have 
no especial value excepting perhaps as curi- 


osities, 

are : 



1. 

Ccesium. 

14. 

Rhodium. 

2. 

Cerium. 

! 5 - 

Rubidiian. 

3- 

Columbium. 

16. 

Ruthenium. 

4- 

Davyum. 

i7- 

Samarium. 

5 - 

Decipium. 

18. 

Scandium. 

6. 

Didymium. 

19. 

Selenium. 

7- 

Erbium. 

20. 

Tantalum. 

8. 

Galliujn. 

21. 

Tellurium. 

9- 

Gluci?ium. 

22. 

Thallium. 

10. 

Indium. 

2 3- 

Thorium. 

11. 

Lanthanum. 

24. 

Ytterbium. 

12. 

Norwegian. 

2 5 - 

Yttrium. 

x 3- 

Osjfiium. 




Besides the seventy elements above enu¬ 
merated, there are some ten or more ex¬ 
tremely rare metals (actinium, gadolinium, 
germanium, helium, holmium, idunium, lime- 



INTRODUCTION. 


15 


nium, mosandrium, neptunium, philippium, 
terbium, thulium, etc.), whose existence is 
not yet quite satisfactorily proven. 

In order to ascertain the value of an ore, it 
is necessary to determine the percentage of 
the metal or metals which it contains. 

This is the first thine to be done—an after 
consideration is the question of the presence 
of other ingredients which may injuriously 
affect the value of the ore or product. 

There are two general methods, known 
respectively as assaying and analysis , whereby 
we may test an ore to learn its composition. 

A comprehensive definition of assaying is 
to call it that branch of exact science which 
enables us to find out of what a substance is 
composed and the proportions, by means of 
dry re-agents and heat. 

On the other hand, analysis is that branch 
which effects the same results mainly by the 
use of wet re-agents, with or without the aid 
of heat. 

In spite of this distinction, wet assays , as 
opposed to dry or fire assays , are continually 
spoken of ; still, to be as consistent as possi¬ 
ble, the terms assaying and analysis, as defined 
above, will be used throughout this work. 





i6 


INTRODUCTION. 


The greater number of the processes given 
in this little book come under the former 
heading, while analysis proper is employed 
in only a few cases. 

The following metals are sought for in ores 
by assaying : antimony, bismuth, cobalt, cop¬ 
per, gold, iron, lead, nickel, platinum, silver, 
tin and zinc. 

It is the object of this manual to treat only 
of gold, silver, copper and lead. For informa¬ 
tion concerning the assaying of the remaining 
metals just mentioned, the student must seek 
it on page 434, among the various works on 
assaying there quoted. 



PART I. 


APPARATUS AND RE-AGENTS. 



MANUAL OF ASSAYING. 


PART I. 

APPARATUS AND RE-AGENTS. 

CHAPTER I. 

APPARATUS USED IN ASSAYING. 

It is as true of the art of assaying as of 
any other, that “good work requires good 
tools.” While many of the latter can be 
dispensed with by the skilled assayer, it is 
often convenient, if not absolutely necessary, 
for the unskilled to have the best utensils for 
the work required. 

I shall therefore give an exhaustive list of 
apparatus needed for the processes herein 
described, but shall try to avoid mentioning 
many implements which are not essential 

*9 



20 


MANUAL OF ASSAYING. 


IMPLEMENTS FOR PULVERIZING, SAMPLING, ETC. 

Iron Mortars and Pestles .—Two sizes of 
mortars are handy, a large one 11 inches in 

diameter, and weighing with pestle about 35 
pounds (2 gallons capacity), and a smaller 

one of 5 inches diameter and 7 pounds weight 
(i gallon capacity). Instead of both, a 
medium size, 8 inches diameter, in 
weight about 19 pounds (1 gallon 
capacity), may be employed. They 
may be either bell or urn-shaped. 
Care should be taken to remove 
all ore from the mortars after grinding. Gen¬ 
erally an old towel, rag, or even paper, will 
suffice to do this, but occasionally washing 
must be resorted to. Dry thoroughly after 
the latter operation. Triturating with dry 
sand often answers the purpose. When not 
in use let the mortars rest mouth 
downward. 

Mortars of various sizes can 
also be obtained with two oppo- 
Fig. 2. sitely situated projections, to serve 














APPARATUS USED IN ASSAYING. 


2 I 



either as handles for carrying, or as trunnions 
for turning over and dumping contents. Fig. 
2 represents this pat¬ 
tern. 

To ease the labor 
of lifting a heavy 
pestle, an arrange¬ 
ment similar to that 
shown in fig. 3 is 
recommended. This 
particular form is 
that which was in 
use in my own lab¬ 
oratory, where it al¬ 
ways gave satisfac¬ 
tion. 

The spring does 
not perceptibly add 
to the force required 
to strike a crushing 
blow, but does ma- Fig - 3 - 

terially aid in lifting the pestle. It (the 
spring) is 18 inches long (when unstretched) 































































































22 


MANUAL OF ASS A YING. 


in coils of if inches diameter, made of the 
best steel of f inch diameter, and painted 
with asphalt black as a protection against 
rust. It is connected to the bracket by a 
strong and flexible cord. The supporting 
bracket or hook is of J inch malleable iron. 
The distance of the eye from the wall I have 
made 13 inches, but it can, of course, vary to 
suit the circumstances. When not in use do 
not keep the spring taut, but let the lower 
end be hung loosely from a hook in the wall. 

Instead of the above contrivance, a spring¬ 
board of hickory, 3 inches wide, ^ to 1 inch 
thick, and 10 feet long, the further end firmly 
fastened, the free end connecting by a strong 
rope with the pestle, will do. 

Any assay laboratory, whether permanent 
or transient, will require at least one of the 
three sizes of mortars specified. For fixed 
laboratories, and where the quantity of ore to 
be crushed is considerable, a very large mor¬ 
tar, 18 inches deep and 12 inches wide 
(weight about 150 pounds), to stand on the 







APPARATUS USED IN ASSAYING. 


Boor, is very valuable. The pestle accom¬ 
panying it is 3 feet long, and weighs about 
18 pounds. The striking end is usually flat¬ 
tened out to a width of from 4 to 6 inches to 
cover more ore at a blow, and also to prevent 
the flying out of the crushed material. To 
use, the assayer stands over the mortar, 
grasping the pestle with both hands. 

The spring or spring-board arrangement 
can likewise be applied to the pestle of this 
mortar. 

To prevent pieces of ore which are being 
crushed in the mortar from flying out, it is a 
good plan to cut a piece of wood, pasteboard 
or tin of a circumference somewhat larger 
than that of the top of the mortar, with a 
hole in the centre large enough to admit of a 
little play to the pestle, and to lay this on top 
of the mortar while at work. 

Crushers .—These are intended to take the 
place of the mortar and pestle for crushing 
comparatively large quantities of ores. For 
small samples the mortar will do very well, 






24 


MANUAL OF ASSAYING. 


but for say 20 pounds and upward, some sort 
of a crusher will be a desideratum. Espe¬ 
cially will it be needed in a large assay labo¬ 
ratory. 




We are pleased to illustrate the “Taylor 
Patent Rock Fine Crusher,” in full in fig 4, 
while fig 5 outlines the operating parts. 

Both jaws are faced with hard white iron, 






























APPARATUS USED IN ASSAYING. 


25 


the lower parts of which are plain surfaces, 
between which the ore is crushed fine. The 
stationary jaw has its lower plain surface at 
an angle to the upper or corrugated surface. 
Lower part of this jaw is adjusted by a screw 
shown under the hand, to crush fine or coarse. 
The movable jaw is operated by the hand 
lever, and has its corrugations horizontal, to 
facilitate the forcing the ore down at each 
stroke of the lever. This jaw has a vertical 
and horizontal motion. 

The lever has a rubber covering where 
grasped by the hand, and a rubber cushion 
where it strikes the bed-piece, to prevent jar 
and noise. 

These jaws are 3 inches wide and open at 
the top 1 yl inches, consequently a piece of 
rock 3x1^ inches can be crushed. With the 
lower part of jaws set at one-tenth inch apart, 
40 pounds of the hardest rock can easily be 
crushed in one hour, and 20 per cent, of this 
will then go through a No. 60 sieve. I hen 
screw up machine and soon run through the 



26 


MANUAL OF ASSAYING. 


balance to No. 60 or finer. This machine 
crushes so much faster than the hand mortar 
and pestle, because of the great leverage and 
power, and because the fine crushed rock 
always drops away; whereas with mortar and 
pestle the fine is always in the way, and 
deadens each blow of the pestle. 

This crusher can be used in crushing old 
crucibles, as well as for working up specimen 
ores, and is as equally useful to the pros¬ 
pector and sampler, as to the assayer. Its 
cost is $25.00 (£ 5, 3 sh.), and weight is 

95 lbs - 

For laboratories where a large quantity of 
ore is frequently to be crushed, I can heartily 
recommend the Gates crusher, shown in fie. 
6. It requires power. 

The operative mechanism of this machine, 
as seen in the engraving shown herewith, 
consists of a breaking head in the form of a 
frustrum or cone, placed vertically with the 
larger end of the cone toward the bottom or 
discharge point. The breaking head is 





APPARATUS USED IN ASSAYING. 2J 

mounted upon a strong forged steel shaft, to 
which motion is imparted through bevel gears 
and an eccentric box. Power is transmitted 
to the machine through the driving pulley seen 
at the left of the picture. The surface of the 
conical breaking head is either fluted, as seen 



Fig. 6. 


in the specimen head removed from the in¬ 
terior of the casing, or, when a very fine pro¬ 
duct is desired, the head is made smooth. 
The interior face of the removable casing is 
smooth, and the coarse material fed in from 
above is continuously broken by being crushed 































'28 


MANUAL OF ASSAYING. 


between the head and concave facing, and 
the space between the crushing surfaces grow¬ 
ing continuously smaller, it is discharged from 
the bottom in fragments of any desired de¬ 
gree of fineness, the degree depending upon 


Fig. 7. 

the adjustment of the head, which adjust¬ 
ment is effected by a powerful screw at the 
bottom of the shaft. 

Fig 7 illustrates the Bosworth Crusher for 
laboratory use, and which runs by either hand 
or power. It has been highly praised. 

























































apparatus used in assaying. 


29 


Pulverizing Plate and Rubbers .—These are 
so useful and convenient that they can hardly 



Fig. 8. 


be dispensed with ; in fact, if much assaying 
is to be done, they will become absolutely 
necessary. They are represented in fig. 8. 
The iron plate, which should be perfectly 
true and have a smooth surface, is made of 
varying dimensions, as 12x12, 18x24, 23x24, 
24x24, 24x30 and 24x36, in inches. It is 
made with no protecting rims, or with rims at 
the sides only (as figured), or with a rim at 
each side and at one end, leaving one end open. 
In some cases the side rims gradually shallow 























30 


MAX UAL OF ASSAY l NO. 


from the back to the front. The size I use, 
and with which I have no fault to find, is 
18x24 inches (inside measurement); thickness 
of bottom, 1 inch ; rims, inch wide and 1-^ 
inches high ; weight, 150 pounds. 

(The only improvement I can suggest would 
be to have the back corners rounded instead 
of being right angles, in order to facilitate 
the removal of pieces of ore and the dust. 
Or the rims might be cast at an angle of say 
30° instead of being perpendicular to the 
surface.) 

The rubber, rocker, pulverizer, grinder, 
muller, bucking-hammer (by which various 
names it is known), to go with above plate, 
is 8 inches long and 4 wide ; thickness at 
ends, ij inches; in centre, 2J ; surface true 
and smooth ; weight about 14 pounds. Other 
rockers made are, in general dimensions, 4X5, 
4X5y, 4x6, 6x7 and 8x10 inches. 

An axe-handle is fitted into the socket on 
top of rocker, and then it is ready for use. 

The operation of grinding, or rubbing, or 



APPARATUS USED IN ASSAYING. 


3 T 


pulverizing is described under the treatment 
of the ores in Part II. 

When a very hard ore is to be pulverized, 
it can much more quickly be finished with an 
8X10 rocker, weight 60 pounds. The addi¬ 
tional weight and greater width have a marked 
effect. An intermediate size of about 30 
pounds’ weight would not be amiss. 

The plate can be placed upon a stout table, 
but it will be better in the long run to have 
constructed for it a special and substantial 
frame-work, as the long continued rubbing on 
the plate will eventually dislocate any ordi¬ 
nary table. The frame can have vertical legs 
as shown in the cut, or can have them set 
with an angle of a few degrees’ spread at the 
floor to which they should be firmly screwed, 
using L-shaped plates of iron as the holders. 
Additional strength may be secured by insert¬ 
ing a thick shelf at about six inches from the 
floor, and this can serve as a resting place for 
the mortars where they will be out of the way. 

In Mr. S. A. Reed’s laboratory the plate is 



32 


MANUAL OF ASS ATING. 


set at an angle inclining toward the operator 
so as to allow of more effective pressure at 
the bottom, and slipped under the front end 
of the plate is a trough or gutter of sheet-tin 
or zinc, as shown in the figure. Its object is 
to catch any particles that may roll down the 
plate, and after the sample has been pulver¬ 
ized, the whole of the powder is brushed down 
into it. The trough is easily detached from 
the plate and its contents can then be brushed 
into a sieve. This simple device may replace 
one of the zinc sifting pans spoken of else¬ 
where. 

Sample Shovels .—A pitch-fork with each tine 
transformed into a narrow trough would give 
a fair idea of the appearance of one of these 
shovels. A better form consists of two troughs 
from four to six inches deep united, with a 
space between, and provided with a long han¬ 
dle. These implements are more needed in 
sampling works proper than in the ordinary 
laboratory. 

Samplers (also known as dividers). — One 





APPARATUS USED IN ASS A TING. 


33 



form of these is shown in fig. 9, 


and consists of a frame with 


partitions running lengthwise 


Fig. 9. 


at equal distances apart, and 


having each alternate space covered at the 
bottom. It is made of tin or copper, and it 
is well to have three sizes. A second pattern 


is represented in 
fig. 10. The first 
form, however, is 
preferred, as being 
more durable. 



Fig. 10. 


To use either, sprinkle over and across the 
broken ore to be sampled, and retain that 
which catches in the troughs, 

A pulp is sometimes sampled by the use of 
a sampler of tin, having troughs | inch in dia¬ 
meter and y 3 g- inch apart. I o use, sprinkle the 
sample across, over a piece of clean paper, 
and separate that which goes between the 
troughs from that which catches in them. Af- 
ter putting aside the latter portion, sprinkle 
across the sampler the former portion, and so 







34 


MANUAL OF ASSAYING. 


continue until a quantity is obtained about 
sufficient for assay. 



Fig. ii. 


Ore Sampling Machines .—We are pleased 
to illustrate and describe the ore sampling 
machine invented by Mr. H. L. Bridgman, 




































































































































































APPARATUS USED IN ASSAYING. 


35 


for use in assay offices, sampling and smelting 
works, stamp mills, etc. 

This machine is a modification of the large 
one, which is doing excellent work. Its par- 



FlG. 12. 


ticular field of usefulness is the quick and cer¬ 
tain cutting down of the miscellaneous small 
samples, (from five pounds to five hundred 
pounds in weight,) that are constantly being 
received by all assay offices. It will handle 


























































































































































































































^6 MANUAL OF ASSAYING. 

J 

anything from the finest assay pulp to crushed 
material of one-half inch or more in size. It 
is a very decided improvement over any of 
the present methods of quartering, or cutting 
down with sample shovel or tin sampler. The 
method of operating is as follows: 

The material is fed either by hand, or (with 
large lots,) from a suitably supported bucket, 
into the funnel “F,” the divider “D” being 
first set in rotation by hand, clock work or 
any convenient power. The divider gives, as 

will be seen by inspection of the drawing, 

* 

eight cuts to the revolution, four being deliv¬ 
ered to the funnel i, and four to the recepta¬ 
cle 2; that is with uniform flow and speed, 
cutting the material in half. The divider may 
easily run 100 revolutions per minute, giving 
in that time 800 cuts, a very much greater 
distribution and division than can be secured 
in any other way. The rejected sample passes 
down the outlet to “0-2,” the retained por¬ 
tion through the outlet “ O-i,” both into suit¬ 
able vessels. The retained portion, should it 



A PPA RA T US USED IN ASS A1YNG, 


37 


be too large, may be cut again and again, 
until of suitable size. The operation is very 
accurate and very rapid, being about as fast as 




Fig. 13. 


the material will flow through a one inch spout. 

Ore Mixer and Divider. —Fig. 13 clearly 
shows this handy little piece of apparatus, also 





































































3« 


MANUAL OF ASSAYING. 


devised by Mr. H. L. Bridgman. We quote 
from the inventor: 

“This apparatus entirely obviates the tedi¬ 
ous and frequently inaccurate methods (usu¬ 
ally with oil cloth and spatula) now in general 
use, for mixing and dividing the ground 
samples of ore, matte, slag and other similar 
material. An experience of several months 
has shown a very decided improvement in 
accuracy, speed and general convenience over 
the old way. 

The operation is as follows: The ground 
material is introduced into the large, covered 
funnel, (mixer,) the outlet being first closed by 
thumb or finger as may be most convenient. 
Funnel and contents are then well shaken for 
a few minutes, and then, with opened outlet, 
passed to and fro over the set of distributing 
funnels (divider) and bottles as shown. With 
very finely ground or very light material the 
flow may be assisted by a slight shaking or tap¬ 
ping with the hand. The little skill necessary 
is readily acquired. 





APPARATUS USED IN ASSAYING. 


39 


The mixer will also be found very useful for 
the prompt and thorough mixing of crucible 
assay charges, and all other work of similar 
character. 

To test the efficiency of the mixer, a lot of 
6 assay tons of litharge, 3 assay tons of soda, 
and assay ton of argols was taken, well 
shaken, divided by weight into three lots of 



Fig. 14. 


3 P4 assay tons each, and these charges fused 
separately in crucibles. 1 he resulting lead 
buttons weighed 53,436, 35,416 and 53,398 

grammes.” 

Fig. 14 illustrates “Buck’s Patent Amal¬ 
gam Mortar,” or laboratory “arrastre.” It 
may be used in place of the grinding plate. 







40 


MANUAL OF ASSAYING. 


Sieves .—A sieve of 80, 90 or 100 meshes to 
the linear inch is necessary. Such sieves are 
furnished of 5, 6, 7, 8, 9, 10, 12 and 15 inches 
diameter (6 to 8 inches is a good size), of 
copper or brass wire in a wooden frame. 
Those composed of horse 
hair are apt to deteriorate. 

The box-sieves 
in brass are de¬ 
picted in figs. 

15 and 16. 

A sieve which 

Fig. 15. Fig. 16. 

is better than 

the ordinary wood-bound pattern is one that 
is pressed or moulded out of the sheet gauze, 
and with no wooden rim to retain pieces of an 
assay which may afterward fall out to con¬ 
taminate a succeeding assay. It would 
require but little of a rich ore to make 
pf a worthless one appear valuable by the 
fig. 17. above accident. Fig. 17 shows the 
idea. 

If the system of sieving and sampling that 

































































APPARATUS USED IN ASSAYING. 


41 


I speak of under the sampling of ores is 
adopted, there will be required a further set 
of four sieves of 2, 4, 8, and 16 meshes re¬ 
spectively, each 10 inches in diameter, and 
with frames of wood 3J inches deep. 

A 40-mesh sieve is useful for sieving cer¬ 
tain chemicals, and two common flour sieves 
are wanted for bone-ash and granulated lead. 

Zinc Sifting Pans. Fig. 18.—These will be 



Fig. 18. 


found convenient, and are better than paper 
for sifting over. A pair is necessary, the 
material sheet zinc. Length in full 31 inches, 
of body 25 inches, of neck 6 inches, width of 
body 12 inches, of neck 2 inches, height of 
rim 2f inches, with upper edge turned over 
heavy iron wire. 

Spatulas and Spoons .— By a spatula we 
mean an instrument shaped somewhat like a 































































42 


MANUAL OF ASSAYING. 


table-knife (fig. 19), and used for mixing 
paints, ores, charges, etc. It may be of iron, 
steel, copper, platinum, silver, ivory, horn, 
porcelain or glass. A large one of steel 
or iron (such as painters use), length in full 
ioj inches, blade 5^ inches long by ij 
wide, is a very good size for mixing ores 
and crucible charges. For weighing out ores 



Fig. 19. 


and mixing scorification charges, a smaller 
one of steel, length 6 inches, blade 3x1 inch 
is useful. 

Two or three horn spoons, with or without 
handles, are serviceable for various purposes. 


SCALES AND BALANCES. 

Two balances will be sufficient for the 
ordinary work of the assayer; a small one 
for weighing fluxes, ores, lead buttons, cupels, 
etc., and a more delicate one for very accu- 















APPARATUS USED IN ASSAYING. 


43 


rately weighing*the gold and silver beads 
and gold residues. 



Fig. 20. 

Scales for Pulps and Fluxes. —Considera¬ 
ble latitude can be allowed in the choice of 
such scales. Balances can be procured carry¬ 
ing 2, 5, io, 20 or 30 ounces and upward, and 
ranging in delicacy from of a grain to 1 




















































































































































































44 


MANUAL OF ASSA TING. 

grain. For descriptions, illustrations, and 
prices of these and others, see the lists of 
the various manufacturers. 

Not wishing to puzzle the student too 
much, I specify but four: 

Fig. 20 represents as satisfactory a pair as 
can be wanted. It has a spirit level and two 
thumb-screws, movable scale-pans (3*4 inch 
diameter), and when it is to be transported, 
all the parts on the box can be packed in the 
drawer. Its capacity is 10 oz. (about 311 
grammes), and it is sensible to ¥ V °f a grain 
(about 3^ milligrammes). Its cost is $22.00, 
(£4 1 os.) (See Becker’s list, No. 19.) A 
glass case in which to keep the scales is a 
good thing to have, and costs $6.00, 

{£' 5 s -) 

Troemner makes a similar balance, capac¬ 
ity 16 oz., sensibility ^ grain, diameter of 
pans, 4 inches, price $18.00 (£3 14s.) (See 
Troemner’s list, analytical scale No. 2, fig. 22.) 

A still cheaper, but satisfactory balance, 
similar to the preceding, is likewise furnished 



APPARATUS USED IN ASSAYING. 


45 


by Troemner, capacity 8 oz., sensibility 
grain, diameter of pans 3^ inches, price 
$15.00 (^3 2S. ) It is represented in fig. 21. 
The objections to it are that it lacks the spirit 
level and adjusting screws, so that it is not 
always easy to get it into perfect equilibrium. 



Fig. 21. 


Directions for Setting-zip and Testing .— 
The various parts of the scales shown as fig. 
20 come wrapped and packed in the drawer 

beneath. They should be carefully unwrapped, 
rubbed a little, if necessary, with some soft, 

clean and dry buck or chamois skin, and put 
into place in the following order: 

A brass wire, somewhat U-shaped, is to be 

































46 


MANUAL OF ASSAYING. 


run up from the under side of the top of the 
box stand through two holes. The ends of 
this wire pass through two holes in the base 
of the pillar (which is now standing on the 
box), and are there held by two screws, 
shown in the cut. Next the swinging needle 
(also variously known as the index needle, 
needle indicator, indicating rod, index pointer 
or pointer) is firmly screwed on to the centre 
of the beam, and the latter placed on the 
knife edges in the socket on top of the pillar. 

Upon the knife edge at each end of the 
beam is placed one of the little frames or 
stirrups having a knife edge and hook, the 
latter to point forward. It will be observed 
that each end of the beam and each stirrup is 
marked with one or more dots. They must, 
therefore, be put together appropriately, that 
is, the stirrup with say two dots is to be 
placed on that end of the beam which also 
has two dots, and so on. The wire frames 
that support the scale pans are now taken, 
the brass piece at .bottom of each swung out 



APPARATUS USED IN ASSAYING. 


47 


at right angles to the wires, and the frames 
suspended from the hooks at end of beam. 
The pans can then be placed in their proper 
positions. The leveling screws, shown at the 
front corners of the box, are now put in place, 
and the scale is ready foi testing and after¬ 
ward for work. 

To test, turn the leveling screws until 
the bubble of air in the spirit level is at rest 
in the centre of its circular case ; push down 
the lever shown in front of the graduated 
scale, thus allowing the pans to swing freely, 
and gently vibrate the needle by directing a 
slight puff of wind from the hand upon either 
pan. The needle should vibrate to the 
same distance on either side, less a small 
fraction every time due to the decreasing 
momentum, and when it has finally come to a 
condition of perfect rest it should be exactly 
in front of the central division of the gradu¬ 
ated ivory scale. 

If the scales are not in good order there 
are no means of adjusting or correcting (save 



48 


MANUAL OF ASSAYING. 


such as the natural mechanical ability of the 
owner may suggest), and the best plan would 
be to exchange them for a more perfect pair. 
This is not likely to be the case, however, 
more especially since such scales are not 
required to be very delicate. 

The directions I have given above for the 
setting up of the scales shown as fig. 20 will 
apply, slightly modified, to any other and 
similar pairs. 

Whatever pair be used, it is advisable to 
take two large watch glasses, in diameter a 
trifle less than that of the scale pans, and file 
down one or the other till they balance each 
other perfectly. Weigh all charges in these, 
thus avoiding any danger of corrosion or at¬ 
trition of the scale pans. 

A soft brush should be employed to brush 
out the contents of the glasses. 

It is a good plan to always place the weights 
in one pan (the right-hand one), and whatever 
is to be weighed always in the other. 

In case many crucible assays are to be made 



APPARATUS USED IN ASSAYING. 


49 


(requiring the weighing of many fluxes), a 
great deaf of wear and tear of the balances 
described can be avoided by substituting 
hand-scales , which are 
cheap and serviceable. 

They are made with 
brass beam,from which 
horn scale pans are 
suspended by means 
of silk threads (fig. 

22). They can be se- 

7 Fig. 22. 

lected from a dozen 

sizes, the length of beam ranging between 
4 and 12 inches—7^ or 8j4 is best; prices 
$2.75 (iis. 6d.) and $3.00 (12s. 6d). Sup¬ 
port them on a nail by the ring at the top, 
and use them for any and all weighings save 
those of the ores. Of course no watch glasses 
need be used with these scales. Their sensi- 

bility is from Tit to ytt gram. 

Occasionally it becomes necessary to weigh 
large quantities (pounds) of ores, fluxes, etc. 














50 


MANUAL OF ASS A TING. 


Use whatever scales are easiest obtained; I 
need not go into detail concerning them. 

Balances for Weighing Gold and Silver 
Beads —Here likewise is a range of choice, 
and personal preference comes largely into 
play. 

When the assayer intends to travel consid¬ 



erably, the balance now spoken of will be the 
most suitable. Length 9 to 9^ inches, height 
9*4 inches, width from 3 to 4 inches. It packs 
into a light box, and by means of . a strong 
leathern strap can be carried by the hand. 
Total weight, boxed, about 4 pounds. With 
the proper weights this balance will weigh 








































































































APPARATUS USED IN ASSAYING. 


51 


T V milligramme, and by use of the swinging 
needle and ivory scale will indicate milli¬ 
gramme. In and out of case, it is illustrated 
in fig. 23. 

It is made both by Becker (No. 2 of his 
list) and Troemner—the prices, with weights 
(1 gramme 


down to T V mil¬ 
ligramme), be¬ 
ing $75 and $65 
respe ct i v e ly. 
(£ 15 8s. and 

^13 7 s -) 

When the 
balance is not 
liable to be 
moved around 



Fig. 24. 


very often, that shown in fig 24 will serve 
nicely, and is considerably cheaper. The 
needle indicates \ of a milligramme, and each 
pan can bear a load of 25 grammes. Price 
$55.00, (^11 6s.) of either Becker (No. 1) or 
Troemner (No. 1). 






















































5 2 


MANUAL OF ASSAYING. 


A similar but larger and somewhat more 
delicate balance is made by Becker (No. 3— 
price $78.00, ^16). The needle indicates 10 
divisions on the scale for 1 milligramme. The 
greatest objection to all of the preceding bal¬ 
ances lies in the fact that they have no grad¬ 


uated beam 
to carry a rid¬ 
er to show the 
weight below 
10 milligram¬ 
mes, but in¬ 
stead indicate 
it by the de¬ 
viation of a 
needle. The 
following pos- 



-&-<£=\ 


Qli 

Qlin Qii' 







Fig. 25. 


sess this advantage: Troemner’s No. 2 (fig. 
25 of this book) is a fine balance. The beam 
at the right is divided into hundredths , so that 
by means of the rider, a button of T V milli- 
gramme can easily be weighed. And more; 
since the spaces between the To milligramme 






























































APPARATUS USED IN ASSAYING. 


53 


divisions are appreciable, by placing the rider 
% 

half-way between any two, a weight ¥ V of a 
milligramme can be determined. Price of this 
balance, $80.00 (^16 9s). 



Fig. 26. 


There is a still larger balance (Becker No. 5, 
Troemner No. 3—price $95.00, ^19 10s. 6d.), 
which is more delicate and better finished 
than the preceding. 

































































































54 


MANUAL OF ASSAYING. 


Fig. 26 is a good illustration of Troemner’s 
“Extra Fine” new balance (No. 5), which is 
noticeable in having its beam of aluminium. 
Has a double column, with improved new ec¬ 
centric lift, that works smoothly and regularly ; 
beam divided on both ends ; glass case large 
and roomy, with heavy plate-glass bottom ; 
needle indicates forty full divisions for one 
milligramme. Price $175.00. (^36). 

Oertling, of London, furnishes a most ex¬ 
quisitely delicate and accurate balance (No. 
12), represented in fig. 27, which stands very 
high. It is expensive — $175.00 (^36)— but 
where very delicate work is required, as in 
weighing the gold residues from small quanti¬ 
ties of low-grade ores, it is indispensable. 

Notes on Setting-up the Oertling Balance .— 
In mounting this balance, after the mechan¬ 
ism below the floor has been connected with 
the beam supports, and the standards (or cen¬ 
tral pillars) have been screwed in position 
with the thumb screw provided, the beam (with 
its index pointer) is put in its place. This 







APPARATUS USED IN ASSAYING. 


55 


4 


must be done from the top, and care should 
be taken that the pointer is not bent in so 
doing. 



Fig. 27. 






























































































56 


MANUAL OF ASS A YING. 


Now adjust the capstan-headed screws on 
top of the standards in such a manner that, 
when the # beam is raised by turning the 
thumb screw in front, each screw will touch 



the beam at the same moment, and with the 
V-shaped support raise the beam uniformly. 
1 he pointer must also coincide exactly with 
the zero point of the ivory scale. A small 



































































































APPARATUS USED IN ASSAYING. 


57 


pin is furnished with the balance for turning 
the capstan screws. 

Now the pans may be placed in position 
and each pan support adjusted in height by 
means of its screw so as just to touch the pan, 
when the beam has been raised from its bear¬ 
ings. 

Fig. 28 represents the Ainsworth balance, 
a recent but worthy rival to the Oertling. 
In general, it is similar to the latter, but is so 
constructed that any possible warping of the 
case will not affect the working of the bal¬ 
ance. The rider attachment is so arranged 
that any lost motion can be taken up. A 
magnifying glass is adjusted in front of the 
needle to show the slightest deviation. Sen¬ 
sitive to the y-J-g- part of a milligramme. 
Price $175.00. (Is 6 )- 

See the price lists of the manufacturers 
quoted. 

It will be seen from an examination of the 
preceding illustrations that all the delicate 
assay balances are alike in their general con- 





58 MANUAL OF ASSAYING. 

-—“ ---- 9 

struction. Each consists of certain charac¬ 
teristic parts, as herewith described. 

First, a central pillar, or two pillars, firmly 
attached to the floor of the enclosing case. 
Upon the top of the pillar or pillars is a 
plane bearing a V-shaped crotch lined with 
polished steel or agate (preferably the latter, 
in which rests the beam by means of a steel 
or agate knife edge. At each end of the 
beam is fixed a steel or agate knife edge, 
from which hangs a little frame with a steel 
or agate plane, and from the frame is sus¬ 
pended, by a long and thin wire, the stirrup 
carrying the detachable scale pan. 

From the centre of the beam depends a 
long, delicate index needle, which swings in 
front of a graduated ivory scale. 

From the right-hand side of the balance 
case of the Becker and Troemner balances, 
and from both sides of the Oertling and 
Ainsworth, extends inward a movable rod, 
controlled outside the case by a milled screw 
head. This rod manipulates a fine “clothes 



APPARATUS USED IN ASSAYING. 


59 


pin” of wire known as a “ rider,” which can 
be placed on any point of the graduated 
beam. 

By the employment of a simple mechanism 
the beam can be raised from its a^ate bear- 
ings to avoid unnecessary and wasteful fric¬ 
tion or injury by sudden shocks. This is 
done by turning the milled screw head shown 
in front. The scale pans are supported when 
the beam is raised by two little disks coming 
up from below. 

On the top of the index needle is a minute 
ball, which, by being either screwed up or 
down, raises or lowers the centre of gravity 
of the balance, and so either increases or 
diminishes its sensitiveness. 

At each end of the beam of the Becker 
and Troemner balances is a very small milled 
screw head which can be screwed in or out, 
and by them the beam is balanced. On the 
Oertling and Ainsworth, instead of these 
screws, a fine piece of wire is twisted around 
the little ball on top of the beam, and points 





6o 


MANUAL OF ASSA YING. 


forward, and by turning it a little one way or 
the other the same object is accomplished. 

A circular spirit level, or two tubular ones 
at right angles to one another, at the base 
of the central pillar or pillars, will indicate 
whether the balance is or is not level; the 
milled screw heads under the corners of the 
case are to do the regulating. 

The whole mechanism of the balance is 
contained in a wooden frame with glass on 
the four sides. Both the front and back win¬ 
dows slide up and down, and are locked with 
the same screw or key which controls the 
beam. 

Special Directions .—The workmanship of a 
fine balance is as delicate as that of a watch, 
consequently the greatest care should be used 
in setting it up and in handling its various 
parts. Many excellent balances have been 
ruined or greatly injured by pure careless¬ 
ness, as by striking the knives, or by letting 
the beam fall suddenly on the central agate 
bearing, which will destroy the delicately 




APPARATUS USED IN ASSAYING. 61 

ground knife edges, and, as a consequence, 
the high sensitiveness is lost. 

The agate hangers should be placed on 
the beam so that the marks on each corre¬ 
spond— that is, each hanger or stirrup has a 
mark corresponding to one on the knife end 
of the beam to which it belongs, and, as the 
hangers are not made interchangeable, cor¬ 
rect placing should be observed. 

Care must also be used in handling the 
pointer or needle, that it is not bent. Should 
it scrape against the ivory scale when oscil¬ 
lating, lift off the beam, taking hold of it at 
the ends, and lay the pointer on a smooth, 
flat surface and gently bend the pointer down¬ 
ward; then replace the beam and note any 
improvement. If it still scrapes, remove 
beam again and repeat the operation, and 
continue this until the needle will oscillate 
perfectly freely. It is not advisable to have 
the pointer too far away from the ivory scale, 
as it makes it so much more difficult to read 
the result. 




62 


MANUAL OF ASSAYING. 


It must be remembered that all of the bal¬ 
ances described are very delicate pieces of 
apparatus , and should be guarded with the 
utmost care. They should be placed far from 
the heat of the furnace, and even away from 
the rays of the sun, tending to unequal ex¬ 
pansion and subsequent contraction. Shocks 
must be avoided and even continued gentle 
agitation , and they should be kept away from 
acid fumes (particularly those of nitric acid), 
and out of moist atmospheres. By having a 
small vessel filled with dry fused calcic chloride 
always inside the case of the balance, the 
moisture present will be absorbed by it, and 
thus prevent, in a measure, the rusting of the 
steel parts of the balance. When saturated 
replenish. 

These balances are provided with steel 
knives and agate bearings, spirit level and 
set-screws. By means of the latter and by 
observing the spirit level, the balance can be 
placed in a state of perfect equilibrium, and 
it should always be kept in such. To ascer- 




APPARATUS USED IN ASSAYING. 63 

tain whether it is in adjustment, throw the 
rest down, thus leaving the pans free, and 
vibrate the needle by a puff of wind from 
the hand. The needle should go to the same 
distance on either side, less a very small frac¬ 
tion due to the decreasing momentum. If it 
does, the balance is in equilibrium ; if it does 

not, adjust the difference by means of a little 

# 

screw at one end or the other of the beam, 
or arrow in the centre. 

To test its sensibility place a one-centi¬ 
gramme weight in each pan and a rider at 
equal distances on each side of the beam, and 
see if in balance. If not, adjust as before. 
Now move one of the riders one of the small¬ 
est divisions — the balance should respond 
quickly and distinctly, also with one-half of 
the smallest divisions (representing with a 
five-milligramme rider ^ milligramme). 

When not in use, the rest should not be 
left down, and on the other hand, when using 
the balance, it should not be brought up when 
the needle is vibrating, as this tends to throw 



64 


MANUAL OF A SSA YIJVG. 


the knives off the agate bearings, and so work 
injury. 

With these balances, as with the ore scales, 
put the weights always in one pan, the mate¬ 
rial to be weighed in the other. Since the 
rider in most balances is used on the beam 
at the right, it is better to employ the right- 
hand scale pan for the weights. Do not 
leave the weights on the pan for too long a 
time. 

In high, dry altitudes, use care in wiping 
the glass doors of the balance, as electrical 
action can be excited which may affect the 
. accuracy of the weighing. Particularly should 
any rubbing be avoided just before using the 
balance. 

0 

Cover the balance when not in use with a 
thick woollen cloth, or heavy pasteboard box 
lined with flannel or similar material ; this 
to keep out dust. 

A very soft and fine camel’s hair brush 
may be employed to cleanse the scale pans 
or other parts from dust. 



APPARATUS USED IN ASSAYING . 65 


Finally, never use these balances for any 
other purposes than for weighing gold and 
silver beads, small pieces of silver or gold, 

etC * WEIGHTS. 

The assayer needs three sets : 

1 st. A set in the French or metric system, 
ranging from 50 grammes down to 1 centi- 
- gramme (10 milligrammes). Since they are 
not to be used for very accurate work, but 
only for weighing fluxes, lead buttons, and 
other comparatively rough purposes, they 
need not be very expensive — $5.00 to $6.00 
C£i to £\ 5s.) 

2d. A second set of metric weights, to be 
very accurate, their range from 1 gramme to 
T \ milligramme, their use for weighing gold 
and silver beads. Such a set is included in 
the price given for the assay balance for gold 
and silver beads first men¬ 
tioned. Separately, they will 
cost $8.00 to 10.00(^1 13s. 
to £2 is.) Fig. 29 repre¬ 
sents a box of these weights. 




















66 


MA N UA L OF A SSA YING. 


3d. A set of assay ton weights. These 
are important, and should be very accurate. 
Their range is from to 4 A. T., and price 
about $6.00. (£1 5s). 

These weights are simply invaluable on 
account of their use requiring no calculations 
beyond a few multiplications or divisions. 

But this assay ton system of weights seems 
to be one of the bug-bears surrounding the 
art of assaying to many beginners, especially 
those advanced in years and opposed to prog¬ 
ress, and whose knowledge of weights is based 
entirely upon the arbitrary systems known 
as the troy, apothecaries’, and avoirdupois. 
There is no difficulty in understanding it, and 
I think my explanations will make the matter 
clear to all. 

The assay ton system is not restricted to 
any one system of weights — it can be applied 
to any, be it in use in whatever country. 

First, then, to illustrate its use : An assayer 
weighs, of an ore to be tested, A. T. 
(assay ton). As a result he obtains a bead 





APPARATUS USED IN ASSAYING. 67 


of silver weighing io milligrammes. If -J- 
A. T. produces io mgrs. (milligrammes), i A. 
T. of the ore will produce 10x5=50 mgrs. of 
silver, and the assayer reports the ore as car¬ 
rying 50 ounces of silver to every ton. If 4 
A. T. of the ore were used and a 10 mgr. 
button obtained, then or 2\ would be the 
number of ounces per ton of silver that the 
ore would produce. The simplicity of the 
arithmetic, rapidity of calculation, and diffi¬ 
culty of making mistakes are all apparent 
here ; there remains only to explain the con¬ 
nection of the A. T. with our ounces, pounds, 
and tons. 

In this particular case the French or metric 
system of weights is the one employed as a 
basis ; but that is immaterial, as will be shown 
further along. To proceed : 1 ton avoirdu- 
pois=2,ooo pounds avoirdupois ; 1 pound 

avoirdupois=7,ooo grains Troy; therefore, 
1 ton avoirdupois=7,ooox2,000=14,000,000 
grains Troy; 1 ounce Troy=4^° grains Troy; 












68 


MANUAL OF ASSAYING. 


hence 14,000,000 divided by 480 equals 29,166 
ounces Troy in 1 ton avoirdupois. 

Now the assay unit, called the assay ton, is 
(in this case) a weight of 29.166 grammes (a 
gramme being equal to 15.4 grains Troy), or, 
(1 gramme being equivalent to 1,000 milli¬ 
grammes), 29,166 milligrammes. Hence the 
relation of milligrammes to ounces is as 1 to 
1—in other words, a milligramme corresponds 
to an ounce, so that if by assay of 1 A. T. of 
the ore we obtain o^old or silver to the amount 

o 

of 4 mgrs., then, without any calculation, we 
know the ore will run 4 oz. to the ton. 

The above calculation starts out with the 
short or American ton of 2,000 pounds. The 
long or British ton weighs 2,240 pounds, but 
we can use it in like manner as a factor, thus: 
7,ooox2,240=15,680,000; 15,680,000 divided 
by 480 equals 32,666. 

Hence the unit of an assay ton system for 
Great Britain or Canada, based on the ton of 
2,240 pounds, would weigh 32.666 grammes, 
and accordingly as we took fractions or multi- 




APPARATUS USED IN ASSAYING. 69 


pies of it in assaying ores, so would our 
resultant beads of the precious metals be 
fractions or multiples of an ounce per the 
long ton. 

Those who may object to the metric sys¬ 
tem can still use the assay ton system by 
making the unit a weight of 291.66 grains 
Troy, or 326.66 grains Troy. In actual work, 
it has been found that ^ A. T. of the gramme 
system equals 5.83 grammes, equals 90.01 
grains Troy, is a good quantity of ore to 
use in a scorification assay. An equivalent 
amount, or nearly so, in the grain assay ton 
system first given, would be -J- A. 1 . equal to 
97.22 grains. 

The adoption of any system of assay ton 
weights avoids long calculations and the use 
of tables. By employing a whole number for 
the weight, then dividing the result by the 
said number and multiplying the quotient by 
29.166 or 32.666, we obtain the same figures 
as by the assay ton system, but this necessi- 




7 o 


MANUAL OF ASS A YING. 


tates considerable multiplication or the use of 
previously prepared tables. 

Besides the above three sets, it will be 
found desirable to have a fourth set of grain 
weights, which may range between 1,000 
grains and -yjy grain, or 300 grains and 
grain. They need not be extremely accu¬ 
rate. The first set will cost $10 or $11 (£2 
is. to £2 5s.); the second $2 (8s. 3d). It is 
sometimes necessary to weigh a bead, button 
or other object directly in grains, when these 
weights will be handy. 

For large weighings in pounds, the proper 
weights will usually be found to accompany 
the scales.* 

(See tables of weights in appendix.) 

FURNACES. 

There are three distinct and separate ope¬ 
rations to be performed in an assay furnace— 

*If many gold bullion assays are to be made, the assayer will 
find it extremely convenient to have a set of so-called “gold 
weights.” (See the article “ The Assay of Gold Bullion.”) 




APPARATUS USED IN ASSAYING. 


71 


roasting, crucible fusion, and muffle work ( i.e . 
scorification and cupellation). 

In an assay laboratory of any extent, where 
many assays are daily performed, it will be 
advantageous, if not imperative, to have a 
special furnace for each of the above classes 
of work, but ordinarily the assayer can man¬ 
age to get along with one. It is requisite, 
then, that the one selected be adapted to 
carry on all the aforementioned operations. 
As to the particular kind he must consult his 
individual preference—and his purse. I can¬ 
not here describe all the varieties of furnaces 
which have from time to time been devised ; 
all I can do is to speak of a few considered 
the best. 

The heat-supplying medium of a furnace 
may be any one of three kinds of fuel, which 
fact, therefore, will serve to form a classifica¬ 
tion of the furnaces themselves into three 
divisions: 

A. Furnaces employing gaseous fuel. 

B. Furnaces employing liquid fuel. 







MANUAL OF ASSAYING. 


72 

C. Furnaces employing solid fuel. 

Strictly speaking, the heat in any case comes 
from the combustion of a gas, for whether the 
fuel be liquid or solid, the burning matter is 
either the liquid transformed into gas, or it 
is gas driven off from the solid fuel. But the 
distinctions drawn will do well enough for my 
purpose. 

A. Furnaces Employing Gaseous Fuel. 

These are the so-called gas furnaces , mean¬ 
ing thereby that the source of heat is our 
common illuminating gas. But as this fuel 
will not be on hand for the majority of those 
for whom this book is written, they are re¬ 
spectfully invited to pass over the following 
dozen pages. 

The furnaces I am about to describe are 
made by the Buffalo Dental Manufacturing 
Company. This company manufactures fur¬ 
naces for either crucible or muffle work, or both, 
some of which require a blast, others only the 
natural pressure of the gas. The student is 




APPARATUS USED IN ASSAYING, 


73 


referred to their circulars, also to Mitchell, 
pages 79 to ioo. 



Fig. 30. 


































































































































74 


MANUAL OF ASS A YING. 


Figure 30 gives a very faithful representa¬ 
tion of a group of gas furnaces as it was de¬ 
signed by and arranged for myself. 

Its duty is to do roasting, crucible fusions, 
scorification and cupellation. The furnace at 
the left is for roasting sulphurets or other 



ores, for experimentation or actual work. It 
is what is known as a Fletcher No. 163 (shown 
in section as fig. 31), and consists of a fire¬ 
clay body strapped with sheet-iron bands, and 
a burner (No. 16 Fletcher). The opening at 








































































































APPARATUS USED IN ASSAYING. 


75 


the top (protected when not in use by the 
cover shown) is to allow the heat to have full 
play upon the roasting-dish placed on it. 
The heat and flame pass from the burner 
through the furnace and out and up the chim¬ 
ney-pipe. The funnel-shaped pipe over the 
cover is to catch and draw the fumes up the 
chimney. When the burner is lighted a most 
powerful draft ensues, carrying all odors and 
fumes at once away. Both the pipe and hood 
are provided with dampers, controlled by 
small weights. The burner is connected to 
the gas-tap by stout \ inch bore rubber tub¬ 
ing. A cast-iron tripod supports one end of 
the furnace and keeps everything firm. 

Next in regular order (supposing a sul- 
phuret ore to be under treatment) is the mid¬ 
dle furnace, for crucible fusions. It, likewise, 
consists of a furnace and burner. The latter 
is a Fletcher No. 15, of same construction, 
however, as the No. 16. The furnace proper 
(shown in detail in fig. 32), is made in five 
parts, the central section (a cylinder of 



MANUAL OF ASSAYING. 




fire clay), the bed¬ 
plate upon which it 
rests, and which has 
an opening for the 
flame to pass 
through, the cover 
(with handle attach¬ 
ed), and which also 
has an opening filled 
by a plug, all of fire 
clay, and finally a 
plumbago lining, 
rubber tube, chim¬ 
ney connection and 
damper, as with the 


other furnace. 

Finally, at the right, is shown a furnace for 
scorification and cupellation, and which I 
have, I think fitly, designated as the “ Moni¬ 
tor.” Fig. 33 shows it enlarged and uncov¬ 
ered. In form it is almost that of the re¬ 
verberatory furnace, the' movable bricks, when 
in place, being the roof. Looking at it from 






































































APPARATUS USED IN ASSAYING. 


77 


another point of view, it may be described as 
a muffle with the flame as well as the heat 
inside. Its exterior dimensions are as fol¬ 
lows: 20 inches long, 7 inches wide and 5! 
inches deep. In the interior, upon the bot 



Fig. 33. 


tom, are four little wedge-shaped bridges of 
fire clay, which are movable, and upon them 
rests a false bottom or floor, also movable. 
The latter corresponds to the muffle bottom 
of an ordinary furnace, and upon it is done 




























































































78 


MANUAL OF ASSAYING. 


all the work. It is 3^ inches wide by 7^ 
inches long and i inch thick, and has a shoul¬ 
der or bench running across its entire width 
on the end nearest the burner. The cover¬ 
ing bricks, four in number, are each 7 inches 
long by 2f inches wide and if inches high, 
each with a slotted bridge for its convenient 
handling. The burner is the No. 16, Fletcher. 
Similar connections to the first-mentioned 
furnaces. 

The 3-inch stove pipes of all three furnaces 
are fitted into one long horizontal pipe, which 
fits snugly into the chimney. 

The bench or table upon which rest the 
furnaces described, is made of pine, well 
seasoned and firmly jointed, to resist as much 
as possible the warping influence of heat 
and to support the weight of the furnaces 
and table tiles. Its dimensions, not figuring 
on the top, which overlaps 1 inch all around, 
are: 4 feet 6 inches long, 1 foot 7 inches wide, 
and 2 feet 1 inch high plus the thickness of 
the top, which is if inches. A double coat 



APPARATUS USED IN ASSAYING. 


79 


of shellac varnish is its sole ornamentation. 
To the sides and ends of the table top are 
firmly screwed four strips of band iron of 2\ 
inches width and £ inch thickness, and of 
such lengths as to alternately overlap at the 
angles, making smooth joints. The top of 
this sort of wall IS inch above the bed of 
the table. Upon the latter are 114 fire-clay 
tiles, or, rather, clamps, such as are used to 
join house tiles, and having the shape of the 
letter “E” less the middle projection. Their 
average size is 3^ inches by 3 inches across 
and if inches high. They are so arranged 
on the table as to leave a series of six air 
tubes or chambers running its entire length. 
The spaces between the tiles are filled with a 
mixture of plaster of Paris and Venetian red 
rubbed up with water. The latter color is 
also used for the tiles themselves, and some¬ 
what on the fire-clay portions of the furnaces. 

A f-inch bore gas pipe, with proper taps 
and nozzles, is screwed to the front of the 
table. 



8o 


MANUAL OF ASSAYING. 


I have been somewhat lengthy in the above 
detailed descriptions, but have done so for 
the benefit of such as may care to duplicate 
the outfit. 

The manner of operating the furnaces is 
simple. As regards the roasting furnace it is 
merely to shut off the dampers of the other 
furnaces, turn on and light the gas, and regu¬ 
late the heat to suit the particular ore. (See 
under Roasting .) The control of the mix¬ 
ture of gas and air is made by means of the 
milled handle at the burner. 

Next as to the crucible furnace. Remove 
cover, turn gas on full at tap, light, and regu¬ 
late by milled handle. Crucibles that contain 
charges that are to be heated gradually can 
be placed in the furnace as soon as lighted; 
others after the lapse of a few moments, to 
allow the furnace to become thoroughly 
heated. Placing the charges in cold, I have 
made good fusions of refractory ores in 25 
minutes from time of lighting. The furnace 
will take crucibles in size up to the Battersea 




APPARATUS USED IN ASSAYING. 8 I 

“S,” which is 4^ inches across by 5 inches 
deep. Use no covers. 

Finally the “Monitor,” for which I may 
claim, not originality (that belonging to Mr. 
Thomas Fletcher), but merely applicability 
and decided improvements in the form, the 
original one being the roasting furnace already 
described. 

To manage it, remove the covering bricks, 
open the damper and shut those of the other 
furnaces, turn full flow of gas on, light as 
usual, and replace bricks. In from 15 to 
30 minutes the interior will be hot enough. 
Remove one or two bricks nearest burner, 
place charged scorifier on false floor, and 
replace bricks again. When the charge is 
melted, slide aside brick nearest burner, 
and set one of the floor supports diagon¬ 
ally into the furnace, one end resting 
on bridge of floor, the other will protrude 
above the top of the furnace. This is to 
break the flame , and is absolutely necessary in 
order to introduce air for oxidation. In 




82 


MANUAL OF ASSAYING. 


cupellation, the gas is turned down more than 
in scorification. 

The time of performing either scorification 
or cupellation (which see) varies according to 
the nature of the ore, charge, size of button, 
etc., but is about the same as that occupied 
in the use of a coke furnace. 

The consumption of gas is not far from 30 
cubic feet per hour. It is not intended nor 
claimed that this furnace can take the place 
of one required to be run from 10 to 12 hours 
per day, for here, of course, a solid fuel will 
be cheaper, but for small runnings of from 1 
to 4 hours or so it is economical, as are also 
the others. 

For small laboratories, then, the advantages 
of this furnace are many: convenience of op¬ 
erating, whereby the assayer sees every step 
and stage of the operation, and so can tell 
when and where to change or improve ; com¬ 
fort in manipulation, for it does not heat up 
the vicinity of the furnace and the room itself 
(quite a desideratum in the summer time); 




APPARATUS USED IN' ASSAYING. 83 

perfect control of the source of heat, so that 
a higher or lower temperature, a reducing or 
oxidizing effect may be produced in an in¬ 
stant ; entire noiselessness, in which charac¬ 
teristic it is the superior of all blast assay 
furnaces; saving of time, which, for furnaces 
employing coke, charcoal or coal, is spent in 
“ bedding down,” feeding, breaking coke, etc. 
freedom from the annoyances of dust, ashes 
and smoke; absence of waste; and, finally, 
its remaining qualifications, which need not 
be dwelt upon, are simplicity of construction, 
durability and portability. 

The complete plant, as illustrated, costs 
very close to $75.00. (^15 8s.) 

B. Furnaces Employing Liquid Fuel. 

There are many varieties of furnaces that 
come under this heading, their fuel being 
refined petroleum, gasoline, etc. As with gas 
furnaces proper, some are intended for cruci¬ 
ble fusions, others for muffle work ; still others 
are for both. The air pressure in some forms 




8 4 


MANUAL OF ASSAYING. 


is derived directly from foot bellows, in others 
from air compressed by an air pump. 

(Consult the circulars of the Buffalo com¬ 
pany already mentioned for descriptions of 
their furnaces ; also Mitchell, pp. 72 to 78.) 

Fig. 34 represents Hoskins’ Hydro-carbon 
Assay Furnace. 



Fig. 34. 


The apparatus shown in full above has 
now been in practical operation for several 
years in many parts of the country, and is 
past the experimental stage. There are many 
inconveniences and annoyances necessarily 
connected with the use of coke and coal fur¬ 
naces whereas this apparatus does away with 
all dust, ashes, constant replenishing of fuel 




















APPARATUS USED IN ASSAYING. 85 

and a large amount of radiated heat; in fact it 
has all the advantages of a blast gas furnace, 
with the additional advantage that it may be 
forced to almost any extent without the use 
of a blower, and being at the same time auto¬ 
matic. The maximum expense of running is 
about five cents per hour, and in our large 
cities will not exceed three cents. Although 
there has been and is a prejudice against gaso¬ 
line as a fuel, this apparatus, as will be seen 
from its construction, is perfectly safe, and no 
accident can occur except through gross care¬ 
lessness. 


Fig. 35 - 

Fig. 35, P is an ordinary force pump, at 
the bottom of which, at A, is a valve which 
closes automatically upon releasing the pres- 





















86 


MANUAL OF ASSA Y/NG. 


sure from the pump; C is a check valve, 
which closes the inlet to the tank T com¬ 
pletely; F is the filling screw ; V is the vent 
screw, for letting off the pressure when 
through ; H is the pipe leading from the tank 
to the burner D ; E is the burner regulator, 
terminating in a fine point, closing the orifice 
of the burner; S S are packing boxes. Upon 
opening C and pumping a few strokes a pres¬ 
sure is created in the tank and on top of the 
fluid, which is forced through the tubes of the 
heated burner, vaporizing the gasoline, which 
finally issues from the orifice at the end of E 
as a highly heated gas, and burns as such in a 
powerful blast. After once starting, the heat 
of the flame passing through the burner vapor¬ 
izes the fluid in the tubes, and hence the ap¬ 
paratus is automatic; requires pumping up 
only once every quarter of an hour or half 
hour, according to the power of blast desired. 
Its action may be controlled from the heat of 
an ordinary Bunsen burner to that required 
to melt cast iron, etc. 



APPARATUS USED IN ASS APING, 


87 


Fig 36 represents the muffle furnace (three 
sizes, taking Battersea C, F and L respec¬ 
tively), fig. 37 the crucible furnace (two sizes), 



Fig. 38. 


while fig. 38 represents another form of crucible 
furnace (also in two sizes). 

Directions For Use .—Close E, unscrew F, 
and introduce about two quarts of gas¬ 
oline, (of 74 0 Beaum<§,) according to the ca- 


























































































88 


MANUAL OF ASSAYING. 


pacity of the tank. Replace F and close 
V; open C one or two turns, and give three 
or four strokes of pump P, and close C. 
Heat the burner by igniting some of the 
fluid in a suitable vessel placed under the 
burner (an old scorifier will do to hold the 
gasoline) ; when hot enough apply a match 
and open E gradually until the action is more 
or less uniform. If no spray or liquid issues 
from the orifice, the burner is hot enough. 
If not hot enough, burn slowly until no liquid 
or spray issues. When sufficiently heated 
the blast can be made of any intensity desired 
by the use of the pump as above. To stop 
its action, shut the regulator E, or open screw 
V, or both; when not in use the vent V 
should invariably be kept open. The mouth 
of the burner D should be two to three inches 
from the fire hole of the furnace. 

For high temperature and muffle work pro¬ 
ceed as follows : 

First , light as above, and heat inside of fur¬ 
nace to redness at least. 






APPARATUS USED IN A SSA YING. 


89 


Second , place the burner against the inlet of 
furnace. 

Third , turn out the blast with E and im¬ 
mediately turn it on again without lighting it 
(or simply blow the dame out of the burner 
tube), when, if the furnace is hot enough, the 
gas will ignite inside of the furnace. The 
heat can be regulated as in the first method of 
burning. When burning i?iside of furnace 

o o 

there must be 710 flcmie in the burner tube . 

C. Furnaces Employing Solid Fuel .— In 
this class are found the best known furnaces, 
using as fuel, wood, charcoal, coke, hard and 
soft coal, or mixtures of them. The furnaces 
themselves may be divided into two general 
classes, portable and permanent, accordingly 
as they may be intended to be moved about 
or remain fixed. 

I. PORTABLE FURNACES. 

Very many forms have been manufactured. 
Space compels me to reduce the description to 
three ; the Battersea, Bosworth and Brown’s. 




90 


MANUAL OF ASSA YING. 


The Battersea furnace is of fire clay, made 
in sections and bound with iron bands. Fig. 



Fig. 39- 


39 is a sectional-view of the muffle furnace, of 
which the .following sizes are obtainable in 
this country : 



Height , 

Diameter , 

Size of Mufflers , 

Price. 



No . in . 

inches. 

in inches. 









Long. High. 

IVide. 


£ 

s. 


c 

27 

WA 

9 3 H 

5/4 

$25 OO 

5 

3 


d 

28^ 

15 J4 

10 4 

6 

30 OO 

6 

12 

6 

E 

29^ 

16 % 

12 4 

6 

35 00 

7 

4 


F 

30 

'VA 

l 4 5 

8 

40 00 

8 

4 

6 

K 

48 

23 

VS 6 

9 

80 00 

16 

9 




















































































APPARATUS USED IN ASS AT INC. 


9 1 


The Bosworth (Fig. 40) is also of clay, in 
three sections, securely bound. Its construc¬ 
tion is such that it is not liable to crack. It is 
durable, convenient, does much work on little 



Fig. 40. 

fuel, and heats the muffle quickly and evenly, 
It uses a 9x15 muffle, although it can be made 
to use a 10x16, if desired. Price $40.00 

G£8 4s 6d.) 


























































































































92 


MANUAL OF ASSAYING. 


For details concerning the preceding fur¬ 
naces consult the various catalogues and cir¬ 
culars of the manufacturers. 

Browns Portable Assay Furnace. Fig. 41. 
—This furnace consists of a nearly square 
sheet-iron frame 28 inches high, 14 inches 
deep, 16 inches wide, lined with fire brick in 
sections, the interior being smooth and straight 
from top to bottom. The cover is cast-iron, 
and is ridged to lessen the danger of cracking. 
The muffle door is cast-iron, and is fitted with 
a circular opening, filled with mica, that the 
operations going on within the muffle may be 
seen when the door is closed. The draft-doors 
are also of cast-iron, and are provided with 
wheel openings to further regulate the draft. 
The circular holes at bottom are in all four 
sides of the furnace, and serve to keep cool the 
true bottom of the furnace upon which the 
ashes fall. The corners of the castings are 
rounded to prevent breaking. 

The muffle seen in the opening rests equally 




APPARATUS USED IN ASSAYING, 


93 


upon the fire-brick in front and in the rear 
of the furnace, leaving a space of \ inch be- 



Fig. 41. 


tween the end of the muffle and the brick 
to allow the passage of fumes. There is also 
a space for fuel of 4 inches on each side of 
muffle. 

































































































































































































MANUAL OF ASSAYING. 


94 

The grate is formed of cast-iron bars, io 
inches long, i inch wide, 9 in number, resting 
upon a cast-iron frame. 

The space below the true bottom is to be 
filled with fire-brick or sand or other material 
convenient. 

The chimney hole is 5 inches in diameter, 
thus accommodating a stove-pipe of same 
dimensions. The bottom of this hole is 17 
inches from the true bottom of the furnace, 
and 8 inches from the bottom level of the 
muffle. 

There is a handle upon each side of the fur¬ 
nace to allow more convenient handling. 

The furnace will take a J Battersea muffle, 

12 inches long, 6 inches wide, and 4 
inches high. But a muffle, of any of the 
various brands found in the market, of 
dimensions approximating those given, can 
be used. Entire weight of furnace is 155 
pounds. 

The above furnace possesses the following 
advantages; 








APPARATUS USED IN ASSAYING. 


95 


ist. Simplicity. Having no complicated 
parts to get out of order. 

2d. Usefulness. It can be used both for 
muffle work and for crucible operations. 

3d. Capacity. There is no other furnace 
manufactured of similar dimensions and weight 
which can accommodate so large muffles, and 
consequently produce so much work and so 
rapidly. 

4th. Durability. Being made of heavy 
sheet-iron, it cannot be broken by handling 
nor injured by heating. 

5th. Adaptability. Any fuel may be em¬ 
ployed for which the draft of the chimney is 
sufficient. 

6th. Light weight. This furnace weighs 
but r55 pounds, as against 300 to 400 pounds 
of other furnaces. 

7th. Cheapness. It is from one-third to 
two-thirds cheaper than any other furnace 
that will do as good work. Boxed for trans¬ 
portation, $20.00 (£ 4 . 10s. 6d.) 

(See advertisements in the appendix.) 




9 6 


MANUAL OF ASSAYING. 


II. PERMANENT FURNACES. 

Whenever an assayer becomes permanently 
settled in any locality, it may pay him to erect 
a brick furnace, which, under such circum¬ 
stances, possesses some advantages over the 
so-called portable furnaces. 

For descriptions of these, whether to be 
used for roasting, fusion, scorification and 
cupellation work, see Mitchell, pp. 57, 63, etc. 
The various stamp mills, smelting and samp¬ 
ling works, and mining corporations scattered 
throughout the West, have usually perma¬ 
nent furnaces burning coke, charcoal, soft or 
hard coal, which may profitably be imitated. 

Fig. 42 gives a vertical section, and fig 43 a 
ground plan of a good furnace, the front view 
or elevation of which is shown in the frontis¬ 
piece. The illustrations being to scale (-3^) 
need but little explanation. The muffle half 
of the furnace is at the right of each figure, 
the crucible furnace at the left, both con¬ 
structed of fire brick. 





APPARATUS USED IN ASSAYING. 97 


The lower half of the muffle furnace is 
anchored with i x-g- inch wrought iron bars 
and ties, and the upper part with those ixf 
inch. 


Fig. 42. 

The muffle appropriate for this furnace is 
the L Battersea, 15x9x5! inches. Coke or 
coal may be the fuel. 

The above very convenient modification of 
Plattner’s furnace was constructed for Mr. 






























9 8 


MANUAL OF ASSAYING. 


John C Jackson, Metropolitan Block, Chicago, 
and although erected for his especial work, is 
yet suited to the necessities of almost any 
assayer. 



Fig. 43. 


Furthermore, many a peripatetic assayer 
has conjured up a temporary furnace of clay, 
adobe, or home-made bricks, using a tile or 
large crucible fora muffle, to meet an emergen¬ 
cy, and when its days of usefulness were over, 
left it to decay and ruin. On such occasions, 
necessity is indeed the mother of invention. 

FURNACE TOOLS. 

Criicible Tongs .— For placing in, and re- 






























APPARATUS USED IN ASSAY/JVG. 


99 


moving from, the furnace, crucibles. The as- 
sayer will need one large and strong pair, of 
wrought iron, 24 to 36 inches long, the grip¬ 




ping ends of which may be curved or straight, 
like figs. 44 and 45, or tongs can be procured 



of either one of the two forms given in figs. 
46 and 47. Either one, however, of the two 
first mentioned, will do very well. 



























IOO 


MANUAL OF ASS A YING. 


A smaller pair, from 15 to 18 inches in 
length, for lifting small crucibles and large 
scorifiers, for placing lead buttons in the cu¬ 
pels, and for opening and shutting the doors 
of the furnace, is invaluable (fig. 48). 



Fig. 48. 


A still smaller pair of 8 inches in length 
(fig. 49), for managing the 
doors of the furnace, is 
handy, but not absolutely 

J Fig. 49. 

necessary. 

Scorifier Tongs .—The correct shape is here 
given (fig. 50). The length about 24 inches. 




Fig. 50. 

The curved arms fit the bottom of the scori¬ 
fier, the long arm extending across the top. 









APPARATUS USED IN ASSAYING. 


lOI 


The best material for these tongs is 
steel, and they should not possess 
too much spring. Two or three 
sizes should be procured, to accom¬ 
modate the various sizes of scorifiers. 

Fig. 51 represents Judson’s patent 
steel scorification tongs, arranged for 
lifting scorifiers from the rear of a 
muffle without disturbing those in 
front. 

Fig. 52 shows a special and pecu¬ 
liar form of scorifier tongs required 
if the “Monitor” gas furnace de¬ 
scribed on pp. 76-78 is employed, or, 
for that matter, whenever a scorifier 
is to be raised by a perpendicular 
lift. Length about 15 inches, great¬ 
est width, 3 inches, and can be made 
of quarter-inch wire. 



Fig. 51. 



Fig. 52. 

















102 


MANUAL OF ASSAYING. 


Ciipel Tongs .—Several forms are permissi¬ 
ble. A common pattern is shown in fig. 53. 



Fig. 53. 


In using these particular tongs, care should 
be taken to secure a firm grasp of the cupel, 
lest it slip through the tongs and be broken, 
and the bead be lost. On the other hand, 
too much pressure may crush the cupel. 

With these tongs the grip should be made 
nearer the top than the bottom of the cupel, 
for should the operator happen to grasp with 
it a cupel below the latter’s centre of gravity 
(especially when the cupel is soaked with 
litharge), it will probably turn over, again 
giving a chance for loss of the bead of pre¬ 
cious metals. 



Fig. 54. 

I he form next figured (fig. 54) is not 
likely to cause the above accident, nor quite 





















APPARATUS USED IN' ASSAYING. IO3 




Fig. 55 - 

so liable to crush the cupel, and fig. 55 illus 
trates a better pair than either of 
the preceding. 

Fig. 56 represents Judson’s 
patent cupel tongs. 

Whatever pair of tongs is used 
should be of steel or wrought iron, 
light weight with not too strong 
a spring, length from 18 to 24 
inches, and with a strong guide. 

For the “ Monitor” gas furnace 
previously mentioned, and as a 
companion tool to the tongs illus¬ 
trated on page 101 (fig. 52), the 
cupel tongs herewith shown as 
fig. 57 is given. The arm “a” is 
straight, “ b ” is curved to form of 
cupel. Length about 18 inches, 
material quarter-inch wire. 

For considerable of my work 


r 

Fig. 56. 





















104 


MANUAL OF ASSAYING. 




Fig. 57. 


I have used, instead of tongs, the cupel 
shovel (fig. 58), and cupel rake (fig. 59). 
The curve of the latter fits the cupel. By 
means of these two implements, one or two 
cupels can be easily and quickly run in or out 
of the muffle without danger of damage. 
They can be of light weight wrought iron, 
and about 24 inches long. For carrying a 
half dozen cupels at a time, a second shovel 
with the blade six to eight inches long would 
be serviceable. 



O 


Fig. 58. 


All the tongs, etc., just described (with the 
exception, perhaps, of Judson’s, which are 
patented), can be made by any blacksmith, or 
even by the assayer himself by exercising a 
little home talent. 




















APPARATUS USED IN ASSAYING, 


'°5 



ooo 

ooo 

ooo 

V.___ 



Fig. 6o. 




Fig. 59. 



Fig. 61. 



Fig. 62. 


Scorifier or Scorifica¬ 
tion Moulds , Slag Moulds, 
or Pour nig Plates . —Four 
no. 63. forms are here represented. 

Any hardware merchant can provide a 
very good substitute for any of the above 












































io6 


MANUAL OF ASSAYING. 


in the shape of a so-called “ gem-plate ,” gener¬ 
ally with twelve cavities. 

Similar moulds can be procured of heavy 
copper, which has the advantage of not sud¬ 
denly chilling the slag and thus causing it to 
retain small pellets of the lead, but they are 
quite expensive, and if the iron plates are 
warmed before using, they will serve quite 
as well. 

I do not recommend the practice of paint¬ 
ing the interiors of the cups with ruddle or 
chalk washes. 

The utility of scorification moulds is obvi¬ 
ous; by employing them the time of cooling 
is greatly diminished, and the scorifiers can 
(but they had better not) be re-used. 

Large moulds for receiving fused crucible 
charges can be procured (for example a 
plumber’s lead pot), but as mentioned else¬ 
where, unless crucibles are rare, they are 
not necessary. It is the custom in some 
assay offices to pour a crucible fusion into 
one of the cavities of the scorification mould 



apparatus used in assaying. 


107 

with conical cups (fig. 62). The lead but¬ 
ton sinks to the bottom of the mould and 
the excess of slag, fused salt, etc., runs over 
the top and into any convenient receptacle. 
Muffl Scraper .—Shown in fig. 64. Made 



Fig. 64. 


of wrought iron, length 24 inches. The cupel 
shovel spoken of can be used for conveying 
sand or bone ash into the muffle whenever 
lead has been spilled upon its floor, and the 
scraper employed for bringing out the pasty 
mass formed, and smoothing down the sur¬ 
face of the floor of the muffle. 

Pokers .—One long straight one, 32-36 
inches, of 3 /^ inch wrought iron (fig. 65), a 



Fig. 65. 


short one, 18 inches, with end bent, for 
muffle work, and a third ordinary poker, for 
stirring the fire, are desirable. 










ioS 


MANUAL OF ASSAYING. 


APPARATUS USED IN THE FURNACE. 

Muffles .—The term muffle is applied to 
that piece of apparatus figured here in vari¬ 
ous forms, in which are performed the opera¬ 
tions of roasting, scorification, cupellation, 
etc. Muffles are made of iron, plumbago, 
or a refractory mixture (f.e . sand and fire¬ 
clay), most generally the latter. They can be 
procured in the market in almost every con¬ 
ceivable size (the price lists enumerating some 
fifty), besides which they can be made to or¬ 
der of any special dimensions. 

Figs. 66 and 67 show the shapes most in favor; 

the latter being especially 
designed to accommodate 
the “Colorado” crucibles 
side by side. Still other 
muffles are open entirely 
at both ends, so that 
:ir contents can be manip- 
as well from the back as 
from the front. Any muffle can be easily con- 













APPARA TUS USED IN ASSA YING. 


IO 9 


verted into this form by sawing off the closed 
end. 

The size of the muffle employed will be de¬ 
termined by the size and make of the furnace. 

In case the furnace is so constructed that 
the muffle can easily be taken out (and it is 
well to have it out during the firing up and 
first heating), then to avoid danger of crack¬ 
ing it by sudden heat it is best to place it on 
top of the furnace to warm it somewhat before 
putting it in position. 

False floors to the muffle are obtainable, 
and save the real floor from injury due to 
spilled lead, etc. They are made of same 
material as the muffles. 

Crucibles .—These vessels are made of vari¬ 
ous materials : black lead (graphite or plum¬ 
bago), French clay, Hessian sand, charcoal- 
lined (i.e. Hessian sand crucibles with a lining 
of charcoal and molasses), quick lime, a mix¬ 
ture of magnesia and chloride of magnesium, 
alumina, and finally those for very special 
purposes, of porcelain, iron, platinum, gold or 



T IO 


MANUAL OF ASSAYING. 


silver. It is but few of these varieties that 
are needed for the assaying of gold, silver, 
copper and lead ores, and these I now specify. 




Fig. 68. 



Fig. 69. 



Fig. 70. 



Fig. 71. 



Fig. 72. 


The so-called clay or sand crucibles are the 
ones fitted for the assaying of the ores of the 















APPARATUS USED IN ASSAYING . 


I I I 


four metals named. They occur in two forms, 
round and triangular (figs. 68 and 69), with 
covers to match. Almost any size can be 
obtained from some one of the manufacturers. 
In giving the charges for crucible work I have 
generally indicated the sizes of crucibles 
needed. The most commonly used crucibles 
will range between 3^ and 4 y 2 inches in 




Fis. 73. Fig. 74. Fig. 75. FiG.76. 

height, and between 2^8 and 4inches across. 
For an ordinary crucible charge of one assay 
ton and fluxes, a crucible \]/ 2 inches high by 
across will be about right. 

Fig. 70 shows the form of the French clay 
or Beaufay crucible or “fluxing pot.” 

Figs. 71 and 72 outline the forms of the 
Denver Fire Clay Co.’s crucibles. 












I I 2 


MANUAL OF ASS A TING. 


For muffle lead the specially shaped cruci- 
bles figured here (figs. 73-76) are desirable. 
The largest size can also be used for fusions 
of gold and silver ores in muffle. They are 
made in three sizes. Those furnished by the 
Battersea company are known as the ‘ ‘ Col¬ 
orado” crucibles. Those manufactured by 
the Denver Fire Clay Co. are known as 5, 
10 and 20 “gramme,” according to the size 
as shown in the following list, dimensions 
approximate : 

AA, “Colorado,” or “5 gramme,” 2 % inches high; 
2 % inches across. 

A, “Colorado,” or “10 gramme,” 3 inches high; 2^ 
inches across. 

B, “Colorado,” or “20gramme,” 3 1 / 2 inches high; 3 
inches across. 

Roasting Dishes .—These are made of re¬ 
fractory clay or black lead, of the form indi¬ 
cated (fig. 77). They should be 
quite shallow. They are used for 

Fig * 77 - the roasting of ores containing 
much antimony, arsenic, sulphur and zinc. 
They are furnished in sizes ranging from 2 








APPARATUS USED IN ASSAYING. 


113 

to 8 inches in diameter. The 3-inch dish is 
suitable for roasting A. T. The 5 and 6 
inch sizes can be employed with satisfaction 
for open air roastings of 1, 2 or more A. T. 
(for crucible work), in place of the frying-pan. 

Scorifiers .—These articles are made of a 
material similar to that of the clay 
roasting dishes. Fig. 78 shows the 
right shape. They should be some¬ 
what shallow; in texture uniform, and free 
from cracks and holes. 

They can be procured in sizes varying from 
1 inch to 5 inches in diameter. 

The best size for all ordinary scorifications 
is the 2f inch (if the muffle is wide enough 
to admit it). This size takes from ^ to \ A. 
T. of ore, according to its gravity. The 2\ 
inch is well adapted for re-scorifications, that 
is, for reducing in size too large lead but¬ 
tons. It can also be employed when very 
little of the ore is to be worked, say ^ A. T. 

Have the 2f inch in large quantity, with 
one half as many 2\ inch and perhaps a few 








I 14 MANUAL OF ASSAYING. 

2\ inch. For certain other purposes it is 
advisable to have on hand a few of the 3 and 
3J inch sizes. 

As the manufactured scorifiers will stand a 
great deal of rough handling without injury, 
and since they are well made and cheap, it is 
better to purchase them, rather than to 
attempt their home manufacture which is not 
a very easy thing. 

Cupels .—Among the most useful articles 
the assayer possesses. They are employed to 
absorb oxides of almost all the metals save 
those of gold and silver, thus leaving these 
two metals behind in a state of comparative 
purity. Lead is the metal whose oxide, 
litharge, they absorb in great quantity. Any 
substance which will absorb these various 
oxides would do, but for many reasons, burnt 
bones or bone-ash is preferred. Good bone- 
ash is so easily and cheaply obtained that it 
seems a waste of time to more than indicate 
the process whereby the assayer himself may 
make his own supply. In brief, horse or 




APPARATUS USED IN ASSAYING. I 15 

sheep bones are boiled repeatedly in water, 
their organic matter (grease, carbon, etc.) 
burnt away, they are then finely ground, 
sifted and washed. (Mitchell, pp. 133-4.) 

Very good cupels can be purchased in sev¬ 
eral sizes, and when they are good, can be 
safely packed and transported. 

The one chief objection to purchased 
cupels is their expense, therefore ordinarily 
it is cheaper to make them, to do which I 
now give directions: 

The bone-ash which can be obtained in 
bulk and of several grades, is mixed, say one 
pound at a time, with a strong solution of 
pearl-ash (or carbonate of potash) in warm 
water, till the mixture adheres well together, 
though it must not be at all pasty. (The 
right degree of moisture is hard to describe 
but easy to acquire.) When a portion of the 
mixture is squeezed in the hand, it should 
cake together (somewhat like half-melted 
snow) and show the imprint of the fingers. 
Now sift through a common flour sieve, place 



MANUAL OF ASS A TING. 


I 16 

the cupel ring upon a block of wood (having 
a large piece of brown paper spread out 
below all), fill about flush with the surface 
with the sifted bone-ash and strike the 
plunger into the ring four or five times mod¬ 
erately heavily. Turn the plunger around in 
the ring once or twice and push the cupel 
gently out. A little practice will soon enable 
the assayer to turn out perfect cupels. 

The moisture remaining in the cupels can 
be driven out by placing them on the top of 
the furnace after a day’s running, or, what is 
better, by allowing them to dry in the normal 
atmosphere of the room or by exposure to 
the sunlight. Cupels thus slowly dried are 
less likely to crack on using. 

The texture of the cupel, that is, its degree 
of porosity, depending on the fineness of the 
bone-ash and amount of compression, is quite 
important. If too fine bone-ash is used, the 
cupel will crack (or “ check,” as it is some¬ 
times termed), in the muffle ; if too coarse, 
the cupel will absorb silver, causing loss. 



APPARATUS USED IN ASS A TING. 


1 1 7 


Therefore a medium grade had best be 
chosen. The above two difficulties are in a 
measure obviated by making the body of the 
cupel, that is, the lower two-thirds, of coarse 
material, and the upper third of fine. 

If the cupel is too compact, cupellation 
proceeds too slowly; if too loose or porous, the 
cupellation proceeds too rapidly, causing a cer¬ 
tain absorption of silver with the lead. As in 
everything else, experience is the best teacher. 

The form of the cupel is immaterial. Fig. 
79 represents the one which I prefer 
on account of the ease with which it 
can be removed from the mould. 

A cupel with diameter of i y 2 inch is a con¬ 
venient size. 

Annealing Cups .—Shown in fig. 8o. Used 
in the assay of gold bullion. Should 
be well made, light but strong. Vari- 
Fig. 8o. ous sizes can be obtained. 

Annealing Plate .—Employed for annealing 
a number of slips at once, in the gold bullion 
assay. In size about 6 inches' long, 2 wide 



Fig. 79. 









MANUAL OF ASSAYING. 


I 18 

and inch thick. May be made of an old 
muffle floor rubbed down. Can be purchased 
of either fire clay or plumbago. 

APPARATUS OF GLASS AND PORCELAIN. 

Sample Bottle >.—A number of 
these (fig. 81), of two, four, six and 
eight ounces capacity, with wide 
mouths, and cork stoppers, are de- 

Fig 8i s i ra ble for pulverized samples of 
ores. 

Re-agent Bottles .—The dry re¬ 
agents are best kept in wide¬ 
mouthed bottles (known as “salt 
mouths"), glass stoppered, thus 
preventing the admission of dust 
and moisture. 

Wet re-agents in bottles of kind 
illustrated in fig. 82. 

Stone-ware crocks of various 
sizes can be employed instead of 
the bottles, and will, of course, contain greater 
quantities. Fruit-jars with threaded necks 























































































APPARATUS USED IN ASS AT I NO. \ IQ 

and metallic caps will stand transportation 
better than the bottles, and tin cans or wooden 
boxes will pack more closely and last longer 
than either. Circumstances will alter cases 
if the laboratory is to be more 
of a traveling than a fixed 
one. 

Whatever receptacles are 
used should be properly la¬ 
belled. 

Bottles, of course, are nec- 
cessary for the wet re-agents. 

The distilled water can be pre¬ 
served in clean demijohns en¬ 
closed in wicker-work, or in clean stone jugs. 

Wash Bottle. Fig. 83.—To contain distilled 
or pure water. A quart is the best size. By 
blowing in at the opening a y a fine stream 
of water is thrown out through b. 

Watch Glasses. Fig. 84.—More 
correctly known as clock-glasses. 
A pair is desirable to place in the 
scale pans of the ore scales, to keep injuri- 



Fig. 84. 












120 


MANUAL OF ASSAYING. 



Fig 85. 


ous substances away from contact; in diam¬ 
eter they should be slightly less than that 
of the pans. 

Porcelain Capsules or Crucibles .—For hold¬ 
ing the bead of gold and silver 
while being parted. Two sizes 
are convenient, one being 1 inch 
in diameter across top by y inch 
in depth, the other r y 2 inch dia¬ 
meter by iy 6 deep. A good shape is that 
here figured. A dozen of each size will last 
some time. 

Test Tubes .—Used in qualitative tests. It 
is well to have some of four, six and eight 
inches in length. A rack to hold them is 
convenient. Some assayers employ 
them for parting gold and silver 
beads. 

Parting Flasks (or Boiling Flasks). 

—A small flask, capacity ]/ 2 ounce, 
of form as figured, is sometimes used 
for parting gold and silver beads, instead of 
test-tubes or porcelain capsules. At least 



Fig. 86. 















APPARATUS USED IN ASSAYING. 


I 2 I 



three will be needed. Round-bottomed flasks 
are also frequently used. 

Matrasses .—Flasks of the shape delineated 
in fig. 87 and used for the parting of 
gold bullion, are generally termed ma¬ 
trasses. It is quite important for the 
purposes of manipulation that the neck 
Fic. 87. 0 f the fl as k should fit snugly into the 
annealing cups employed. Can be held by 
a wooden clamp. 

Besides the form figured, there are others 
used by assayers in foreign countries. Thus 
one variety is about the same as that in fig. 87, 
but lacking the shoulder. A third pattern is 
similar, but has a lip for pouring. A fourth 
has a very broad base and so on. Whichever 
form works best in practice with any assayer 
will, naturally, be preferred by him. 

Evaporating Dishes .—Are of glass, and 
also of porcelain, the latter being much more 
durable. Used for evaporating liquids to dry* 
ness, or in place of the casserole figured on 
page 123. 






122 


MANUAL OF ASSAYING. 


20 


30 


40 


50 


6n 


70 


BO 


SO 


Graduated Apparatus. — An accu¬ 
rately graduated burette (see fig. 88) 
of 50 c.c. capacity, and several glass- 
stoppered flasks of 1 litre capacity 
(1,000 c.c.), 500 c.c., 250 c.c., 100 c.c., 50 
c.c., etc., will be needed for volumetric 
work. They can be purchased suffi¬ 
ciently accurate for all ordinary de¬ 
mands. Some measuring cylinders 
(lipped), of 10, 15, 25, and 50 c.c. ca¬ 
pacity, not carefully graduated, are very 
useful in measuring solutions for the 
various analyses. 


Fig. 88 . 


Glass Beakers. — 
the copper and 
other analyses, 
chlorination and other 
tests, etc. They should be 
lipped (fig. 89), and pref¬ 
erably of thin material 
to stand heat. Several 
nests may be wanted. 


Will be needed in 



Fig. 89. 





























































APPARATUS USED IN ASS A TING 


123 



Fig. 90. 


Glass Funnels. —For analyses of 

* 

different kinds. Should be of an 
angle of 6o° (fig. 90.) 

Glass Stirring Rods. —Very use¬ 
ful. Cut up a long glass rod into 
various lengths, and round each 
end by holding in a lamp or gas flame for a 
minute or so. 

Flasks. —One will be wanted for the chlori¬ 
nation assay of gold. Several sizes can be 
made use of, for wash-bottles, to retain solu¬ 
tions for any length of time, etc. Should be 
of thin glass. 

Separatory Funnel. —See ‘ ‘ Chlorination As¬ 
say for Gold,” in appendix. 

Casserole. Fig. 91.—Of 
porcelain. Can be put to 
many uses, as small evapo- 

. Fig. 91. 

rations, etc. 

Pipettes. Fig. 92.—A 10 c. c. and a 5 c. c. 



Fig. 92. 


will be required in the copper analysis. They 



























124 


MANUAL OF ASSAYING. 


can be home-made by drawing down to a fine 
opening one end of a glass tube, and rounding 
the other. 


93 


Mortars and Pestles .— Small 
sizes of these are useful in pul¬ 
verizing re-agents, etc. Their 
material may be either glass (Tg. 
3) or porcelain ; shape as represented. 



Fig. 93. 


MISCELLANEOUS APPARATUS. 

Note-books. —Indispensable. Nothing should 
be left to the memory, but everything impor¬ 
tant relating to the assay of an ore should be 
down in black and white. 

The number of the ore, its character, the 
charge for the furnace, conduct in the fire, 
results of the various operations, as shown by 
the crucibles, scorifiers, cupels, slags, buttons, 
beads, etc., and all calculations, should be 
taken note of. 

Gummed Labels .—An assortment of various 
shapes and sizes will be found extremely con¬ 
venient. 








APPARATUS USED IN ASSAYING. 


1 2 5 


Boxes .—Of pasteboard, 5^ inches long, 3^ 
wide, and 2 high, to be used for pulverized 
samples. Paper boxes, tin boxes, paper bags, 
and cloth bags are also used. 

Paper .—Sheets of heavy brown or man ilia 
paper for the mixing of ore samples are neces¬ 
sary. 

Sheets of black glazed paper can be used 
instead, but it is better to reserve these for 
the mixing of charges, as they are a little too 
delicate for rough work. Some assayers use 
pieces of sheet rubber, rubber cloth or oil¬ 
cloth. 

Whatever kind be employed, see that it 
has no holes to allow loss of sample or charge. 

Tissue paper for wrapping up borax glass 
into pellets, and for enfolding minute gold 
and silver beads for flattening, will be needed. 
Filter-paper is indispensable for filtrations; 
also valuable for removing small quantities 
of moisture from the interiors of the porce¬ 
lain capsules in the operation of parting. 





MANUAL OF ASSAYING. 


I 26 

Clean blotting-paper will do for the latter 
purpose. 

The filter paper may be obtained in sheets 
or cut round of any size wanted. 

Brushes .—Several are necessary. First, in 
case the rubbing-plate is employed, a large 
brush, such as is used by painters, is invalua¬ 
ble. 

For brushing charges from the scale-pans 
or glazed paper, a medium size camel’s hair 
is wanted, and for brushing the scale-pans of 
the delicate balances a very fine camel’s hair 
brush is needed. 

Pincers .—A few pairs of varying sizes are 
handy. One of about 8 inches in length, 
strongly made of wrought iron, a 4-inch pair 
of brass, and a third pair with limbs running 
down to a fine point, for picking up minute 
gold and silver beads, will suffice. 

Hammers .—While the assayer can get along 
with one or two hammers, it is better to be 
provided with four or five. A heavy 5-pound 
sledge-hammer, a couple of smaller ones of 



APPARATUS USED IN ASSAYING. 


I27 


about two pounds, one of them having one 
sharp edge and a square face (fig. 94), the 
other with both faces blunt, a small hammer 
for breaking crucibles and scorifiers and flat¬ 
tening buttons, and a ^-ounce sharp-edged 
hammer for trimming small specimens and 
flattening gold and silver beads, are very con¬ 
venient. 



Fig. 94. 


A sharp hatchet for kindling-wood and a 
dull one for breaking coke complete the cate- 
gory. 

Anvils. — A miniature blacksmith’s anvil 
(fig. 95), weighing 10 pounds, and properly 
mounted on a block, will be in constant de¬ 
mand. A simple yet satisfactory method of 
mounting the anvil has been of long-time use 
in my laboratory. An oaken block, 30 inches 













128 


MANUAL OF ASSAYING. 


high by 12 inches through in both the other 
directions, has a frame of 1 inch wood 
screwed to its sides at the top, rising one 
inch above the surface. On the top of the 
block is nailed a half inch thickness of 
rubber belting, leaving one-half inch space 
between its surface and the upper edge of 
the surrounding frame. The anvil is screwed 

o 



Fig. 95. 


down to a piece of 2-inch oak fitting this 
space. The oaken block furnishes a firm 
support for the anvil, the rubber deadens the 
sound of blows, and by lifting off and put¬ 
ting aside the anvil and its bottom, the block 
serves as a convenient table for breaking ores 
in the mortars. An illustration of this is 
shown on p. 21 (fig. 3). 

Another useful form of block and anvil 


























APPARATUS USED IN ASSAYING. 


I 29 


may be easily constructed. Obtain a good 
section of a tree trunk, such as 
butchers use, to be about 36 
inches high and any convenient 
width, as 20 inches. In the cen¬ 
tre excavate a hole somewhat 
smaller than the horn of the 
anvil figured above, and with 
a wooden mallet or block of 
wood and a heavy sledge ham¬ 
mer drive the anvil firmly home. 

A flat plate of steel, if by 1 
\ inch thick, on which are to be 
gold and silver beads, is useful. 

Ring-stand .—This implement, 
made of cast-iron, is useful for 
many purposes; to hold a wire 
triangle that supports the por¬ 
celain capsule used in parting, 
to support a sand-bath, wire- 
gauze, etc. Fig* 97 shows one 
pattern. 

Wire Triangle. — Of twisted 




l inches and 
flattened the 

















MANUAL OF ASSAYING. 


I 3° 



Fig. 98. 


wire (best of platinum), in 
shape as figured, for support¬ 
ing capsules, etc. It may also 
be strung through pieces of 
pipe stems. 

Sand-baths .—Any flat plates of tin or iron 
filled with sand. Their use is to distribute 
the heat around any vessels imbedded in the 
sand. 

Wire-gauze. — Three-inch squares of iron 
wire gauze are used for same purposes as the 
sand-baths. 

Burners , Lamps , and Stoves .—When gas 
can be procured, the Bunsen burner 
(fig. 99) is the best supplier of heat 
for small purposes. By turning the 
ring at the bottom so as to close 
the holes, a light-giving flame is 
produced ; by leaving the holes 
open, there is obtained a heating 
flame due to the more perfect combustion. 
A large alcohol lamp is the best substitute for 
the Bunsen burner. 



Fig. 99. 








APPARA TVS USED IN ASS A TING. I 3 I 

Stoves for burning gas, gasoline, kerosene, 
lard oil, etc., are numerous and varied. One 
of the very best, the ‘ ‘ Dangler Laboratory 
Lamp,” is all we can give space to. Note the 
following directions: Fill the reservoir about 

2 /$ full of gasoline; open 
the air valve and force the 
air into the tank by the 
use of the rubber bulb. 
When sufficient pressure 
is obtained, close valve. 
To light burner, fill the 
drip cup with gasoline by 
opening the middle valve; 
when full, close valve and 
Fig. ioo. light contents of cup and 

when nearly burnt out open valve again to any 
extent required for fire needed. If there is too 
much pressure let some of the air out at the 
valve. Let the air out of the valve instead of 
closing valve on burner. Use 74 ° deodorized 
gasoline. 

Fr\ in? Pan .—Aside from any culinary im- 

























i3 2 


MANUAL OF ASSAYING. 


portance, this kitchen utensil serves a useful 
end in receiving melted borax glass, spread¬ 
ing the latter out that it may cool in a thin 
sheet. 

It is also occasionally employed in the 
roasting of sulphurets, etc., on a compara¬ 
tively large scale. 

In either case coat the pan with chalk or 
ruddle paint. 

Blowpipe .—For testing minerals and for 
fusing gold and silver together. There are 
many forms of this important little instru¬ 
ment, but a plain curved one is as satisfactory 
as any for ordinary blow-piping. They can 
also be obtained in special forms to give a 
“hot blast,” and with a support for the lips, 
whereby the worker may not be easily tired. 
(Consult the works on Blowpipe Analysis.) 

Cupel Moulds .—For making cupels. These 
are made of either steel or brass, but prefera¬ 
bly of the latter, since they do not rust so 
quickly. A mould generally consists of three 
parts, the plunger or pestle, which is convex 





APPARATUS USED IN ASS A TING. 


t -i i 

1 JO 


at the bottom to form the concavity of the 
cupel, the ring into which the plunger partly 
or wholly slips, and a bottom plate upon which 
the ring rests. In some moulds this bottom 
plate is circular and fits into the ring. 

Fig. ioi represents a good form, 
which is of brass, and is furnished 
in sizes that make cupels of and 
inches diameter. It has no bot¬ 
tom plate, but a smooth block of 
hard wood will serve equally well. 
The cupel this mould furnishes has 
its sides at right angles to the base 
(see fig. 79). One advantage this 
Fig. ioi. form of mould possesses is that by 
using more or less bone-ash, cupels of vary¬ 
ing thicknesses can be obtained by reason of 
the plunger sliding in the ring, which is not 
the case with all others. 

A special machine has been devised for 
making cupels, but I am not at all certain that 
it turns them out any better than does the 
common mould, nor more rapidly. If greater 
































134 


MANUAL OF ASS A TING 


pressure is needed than that given by the 
hammer or mallet, a second-hand letter press 
might be utilized by knocking off the upper 
plate and making a few alterations. 

Shears .—For cutting gold and silver bull¬ 
ion, sheet silver, lead-foil, etc. Should be 



Fig. 102. 


strong and have a keen cutting edge. Fig. 
102 represents a good form. 

Scissors for cutting filter papers, etc., will 
be wanted. 

Hand Rolling Mills .—For assayers and 
jewelers, mounted upon cast iron column. 
The rolls are evenly tempered, truly ground 
and finished with a high polish. The gears 
are all cut, cranks of steel, boxes of bronze, 
and the pressure screws of steel, with the 
points tempered. They are made in at least 
eight sizes for hand use (and still larger ones 




















APPARATUS USED IN ASS A TING. 


*35 


for power), with rolls from 2x1 to 4x2^ 
inches, and weighing from 60 to 200 lbs. 
They cost from $30.00 to $100.00, [£6 12s. 6d. 
to £20 IIS.) 



Fig. 103. Fig. 104. 





Fig. 105. 


laboratory. 


Magnifying Glass. —Pocket 
size very useful. 

Magnet .—A small pocket 
magnet will come in play very 
often, both in the field and 
Metallic iron, magnetic oxide 


of iron, nickel, and cobalt are attracted by it. 




























i ^6 manual of ass a ting . 

J • ____ ~ 

Figs. 106 and \oy show the two forms com¬ 
monly used. 



Fig. 107. 


Ingot Moulds for gold, silver and lead can 
be obtained in many sizes and shapes. Some 
of the latter are herein figured. 



Fig. 108. 


Thus fig. 108 casts a bar 1 y£x8 in., and has 
a slide, permitting varying lengths of bar. 
Fig. 109 gives an ingot 4x T 9 6 x3,4, or one 
or a third 8*4 x3xi in. Fig. 110 casts a bar, 
5^2x2^x2 in., with rounded corners. Fig. 
























































APPARATUS USED IN ASSATING. 


I 37 


iii gives an upright ingot, in. 

Fig. 112 is for quadruple sample bars. 



Fig. 109. Fig. iio. 



Fig. iii. 


Fig. 112. 


Steel Alphabets and Figures .—The bullion 
assayer will need these for stamping bullion. 
They should comprise the numerals from o to 
9, an alphabet, and certain 
stamps in one piece, as 
“Gold,” “Silver,” “Fine,” 

“Value,” “Total,” “No.,” 

“Oz.,” and “$.” In size 
the above may vary from ¥ V 
inch to 5/s inch. Steel dies 
with name of mine, company, assayer, etc., 
can be procured as desired. 
































138 


MANUAL OF ASSAYING. 



Bullion Punch. —Fig. 


Fig. ii 4 . 114 shows a very good 

punch for taking a sample from lead bullion. 

Cold Chisels .—One large (1 inch diameter) 
and one small one (yi inch) are useful. 



Fig. 115. Fig. 116. 


Miners Gold Washing Pans. —Fig. 115 
shows one form, material Russia or agate iron, 
seamless, \ 6]/ 2 inches diameter. Fig. 116 



Fig. 117. 


gives full and sectional views of the “Batea,” 
of wood or Russia sheet iron, and from io to 
17 inches diameter. Fig. 117 illustrates the 














APPARATUS USED IN ASSAYING. I 39 


“Miners Horn,” of black hard rubber, and 
Fig. 118 a similar one, of horn. See “Pan 
Test for Gold,” in appendix. 



Fig. 119. Fig. 120 


Scoops .—For ores, quick¬ 
silver or amalgam, etc. Two 
varieties, 5x4^ an d 

5x5^2 in., both Russia iron, 
are illustrated. These scoops 
are useful implements in any 
assay laboratory. 

Filter Stands. Fig. 121.— 
For holding funnels. Wooden 
ones are easily obtained or 
made. An iron ring stand 
can also be used. 



Fig. 121. 























140 


MANUAL OF ASS A YING. 


Burette Stands. — Any simple, neat, and 
convenient form of support for burettes will 
do. A favorite one is made of iron ; the clamp 
of brass with cork-lined jaws. 

Battery , Platinum Vessels, etc .—See “ Cop¬ 
per Analysis.” 

Iro 7 i Retorts .—They are used for distilling 



Fig. i22. 

off the mercury from an amalgam. Can be 
found in sizes ranging from ^ to 24 pints. 
The smallest size will do for ordinary work. 
Fig. 122illustrates a commonly used pattern. 

Chamois Skin or any other fine leather. 
—Used in squeezing out the free mercury 
from an amalgam. 

o 











CHAPTER II. 

RE-AGENTS USED IN ASSAYING. 

Under this heading I purpose to speak of 
those re-agents (or substances which react), 
necessary for the assaying of gold, silver, 
copper and lead ores. I shall tell what they 
are, how they act, when to be used and with 
what object, and, finally, how to prepare 
them when preparation is necessary. 

DRY RE-AGENTS FOR ASSAYING. 

The dry re-agents needed for the assays 
described in this book are seventeen in num¬ 
ber, as follows : 

1. Bi-carbonate of soda. 

2. Carbonate of potash, 

3. Cyanide of potash. 

4. Borax glass and common borax. 

5. Flour. 

6. Black flux substitute. 

7. Argol (or cream of tartar). 


141 


MANUAL OF ASSA TING. 


142 

8. Common salt. 

9. Carbonate of ammonia. 

10. Nitre. 

11. Wood charcoal. 

12. Silica. 

13. Lead (sheet and granulated). 

14. Litharge. 

15. Iron (nails and wire). 

16. Silver. 

17. Sulphur. 

/. Bi-Carbonate of Soda (chemical name, 
hydro-sodic-carbonate).—This is the ordinary 
commercial bi-carbonate, and needs no prepa¬ 
ration, save to be ground free from lumps. It 
is employed in the crucible assays of gold, sil¬ 
ver, copper and lead ores. Its action is de¬ 
sulphurizing (that is, it removes the sulphur 
from ores fused with it, forming sulphide of 
soda), and oxidizing (that is, converting cer¬ 
tain metals, as iron, tin and zinc, which may 
have been in the ores treated, from the metal¬ 
lic state to their corresponding oxides), by 
means of the carbonic acid it contains. Be¬ 
ing so readily fusible, it acts as a wash to 





RE-AGENTS USED IN ASSAYING. 


143 


rinse down from the sides of the crucible any 
matters which may be adhering thereto. 

Finally, it has a most important bearing as 
a flux, meaning that it forms a fusible com¬ 
pound with certain impurities of the ores, as 
metallic oxides, etc. 

2. Carbonate of Potash (potassic carbonate). 
—Ordinary carbonate (not bi-carbonate) of 
potash. Since a mixture of the alkaline car¬ 
bonates (i.e., carbonates of potash and soda), 
is somewhat more fusible than either alone, 
the use of this carbonate is advisable in cru¬ 
cible assays, particularly of gold and silver 
ores. It should be ground to a fine powder 
and kept from the air, as otherwise it would 
rapidly absorb moisture. Its action is the 
same as that of the bi-carbonate of soda. 

j>. Cyanide of Potash (potassic cyanide).— 
The cyanide which is sold in cakes can be 
used, after being pulverized, or, what is bet¬ 
ter, the so-called granulated cyanide, which is 
fine enough for all purposes. In case that in 
form of cakes is on hand, it must be finely 




144 


MANUAL OF ASSA TING. 


pulverized, which ought to be done in the 
open air, using an iron mortar, the top of 
which is tied over and around with a towel. 
Also it is well to breathe through a wet cloth 
wrapped around the head across the nostrils, 
for the cyanide is so poisonous that inhaling 
the fine dust even is a dangerous practice. 
Use the box sieve for sifting. Keep from the 
air, as this salt absorbs moisture therefrom. 

Employed in the lead assay. Action de¬ 
sulphurizing and reducing (that is, taking 
away the oxygen from metallic oxides and so 
reducing them to the condition of metals ; it 
is the reverse of oxidizing). 

4. Borax Glass (sodic bi-borate). — The 
most valuable flux the assayer possesses. He 
employs it both for the crucible and scorifica- 
tion processes for gold and silver ores, and 
the crucible process for copper and lead ores. 
It has a neutral action. The unfused borax, 
in powder, is often used in the lead assay. 

The ordinary borax of the shops contains 
from 30 to 47 per cent of water of crystalliza- 






RE-AGENTS USED IN ASS AIT NG. 


H5 


tion, which must be gotten rid of before the 
borax is fit for use. Borax, on being strongly 
heated, swells very considerably while losing 
this water, and then gradually sinks down into 
a clear liquid, which, on cooling, becomes the 
glass. 

Take a large size sand crucible (“S” of 
Battersea make) and carefully coat its interior 
with either dry chalk or chalk wash. Place 
this in a hot fire, and drop in small pieces 
of borax, letting the swelling subside some¬ 
what after each successive addition. It is 
well not to allow the crucible to become more 
than one-third full of the melted borax, as, in 
spite of the chalk lining, it is liable to attack 
the crucible and run through. 

When thoroughly fused, appearing like wa¬ 
ter, pour into a frying pan coated with chalk 
or ruddle, and let cool. Powder in an iron 
mortar and sift through a 40-mesh sieve. That 
which goes through had best be reserved for 
crucible mixtures ; the moderately coarse re¬ 
maining on the sieve will do for scorifications. 



146 


MANUAL OF ASSAYING. 


A strong iron coffee-mill with teeth or jaws 
close together, will crush borax glass very 
finely, and in much less time than it can be 
done with mortar and pestle. 

An iron crucible can be employed in place 
of the sand one. It will color the borax 
somewhat, which, however, does no damage. 

5. Flour .—Wheat flour is serviceable in the 
lead assay, its action being reducing. But it 
is more commonly employed together with bi¬ 
carbonate of soda, forming what is known as 

6 . Black Flux Substitute .—A mixture of 
ten parts bi-carbonate of soda and three of 
flour. It can be used to great advantage in 
the crucible assays of all of our four metals. 

7. Argot (crude bi-tartrate of potash; when 
pure called cream of tartar or hydro-potassic 
tartrate).—This is a good reducing agent, 
and is much used in the lead assay, and in 
crucible charges for gold, silver and copper 
ores. 

The following list of the reducing powers 
of various reducing agents will be found to be 







RE-AGENTS USED IN ASS A TING. 


T 47 


very useful. The values are approximate 
only, as no two samples of any one listed will 
reduce to exactly the same amount, but for all 
practical assaying they are sufficiently near. 
I have included only those substances which 
are procurable in almost any section of the 
country. 


TABLE OF REDUCING POWERS OF REDUCING 

AGENTS. 

1 part of Will Reduce Parts of Metallic Lead 


Ordinary wood charcoal 

22 tO 30 

Powdered coke 

24 

“ hard coal 

25 

“ soft “ 

22 

Wheat flour 

15 

Corn starch 

ii>£ to 13 

Laundry starch 

11^ to 13 

Pulverized white sugar 

14 M 

“ gum arabic 

II 

Crude argol 

syi to 8 y z 

Cream of tartar 

\Vi to 6 y 2 

See chapter III., iv., pp. 

175-6 for methods 

of determining reducing 
substances. 

powers of above 



148 


MANUAL OF ASSAYING. 


8. Common Salt (sodic chloride).—Ordi¬ 
nary table salt. Very useful in every cruci¬ 
ble assay. It serves somewhat as a protect¬ 
ing cover, and as a wash, bringing down from 
the sides of the crucible adhering metals or 
fluxes. If moist, place in frying pan and 
heat till dry, then crush free from lumps. 

9. Carbonate of Ammonia (ammonic car-= 
bonate).—Of very little importance, save to 
assist in the roasting of certain ores. It ex¬ 
erts a desulphurizing action. To be employed 
as a fine powder. 

10. Nitre or Saltpetre (potassic nitrate).— 
Ordinary saltpetre of commerce. Is a basic 
flux and oxidizing agent, and is used in the 
crucible assays of gold, silver and lead ores. 
Pulverize finely and keep dry. Determine 
oxidizing power as shown on page 176. 

11. Wood Charcoal (carbon, more or less 
impure).—Very valuable on account of its 
reducing and desulphurizing properties. Lt 
exercises the latter action when employed in 
the roasting of antimonial and arsenical gold 








RE-AGENTS USED IN AS SATING. 


149 


and silver ores. Let it be in a fine condition, 
keep dry, and determine reducing power in 
same manner as for argol or cream of tartar. 
(See page 175.) One part of ordinary 
wood charcoal will reduce from 22 to nearly 
32 parts of metallic lead from litharge, 
according to the purity of the charcoal. In 
the scorification assay of certain ores (arsen¬ 
ical, antimonial, etc.), charcoal exerts a 
beneficial action in breaking up the crust 
which sometimes forms on the surface of the 
charge. A few pieces of roughly pulverized 
charcoal introduced into the matrass in part¬ 
ing gold bullion, excite local action and so pre¬ 
vent the bumping of the nitric acid solution. 

There are quite a number of substances con¬ 
taining carbon in varying proportions, which, 
for the sake of their reducing action, might 
be used as substitutes for cream of tartar and 
charcoal, but not one of them is so effective 
as either of the two mentioned, and since the 
latter are so easily obtained, I refrain from 
extending the list given on page 147. 



MANUAL OF ASSAYING, 


ISO 

/^. Silica (silicic di-oxide).—This is a valu¬ 
able acid flux, that is, it is to be used as a flux 
for ores which are basic in character (as calc 
spar, dolomite, barytes, fluor spar, etc.), also 
for ores containing large quantities of iron 
oxides and carbonates and with little or no 
silica. It is required for the assays of cer¬ 
tain ores of gold and silver in both the cruci¬ 
ble and scorification processes, as will be 
shown. The best form in which to use it is 
as pulverized silica (sold very cheaply), since it 
is then in a very fine state of division suitable 
for intimate mixture with ores and fluxes. 
It should be perfectly dry. 

As substitutes, in emergencies, fine, clean, 
dry sand can be used, and some kinds of 
glass (which are silicates of soda or potash, 
with lime, lead, etc.). Lime glass is to be 
preferred, but on no account is lead glass, or 
any containing arsenical compounds or easily 
reducible metallic oxides, to be employed. 
Common window glass and ordinary bottle 
glass, broken finely, will serve, and will be 




RE-AGENTS USED IN ASS AT / NG. I 5 I 

found to be free from objectionable metallic 
ingredients. 

There is no advantage gained in using 
these substitutes, since the pulverized silica 
answers admirably, only it is well to know 
what to make use of, in case supplies run out. 

ij. Lead .—In thin sheets, called lead-foil, 
this metal is occasionally necessary for cupel- 
lations, as described under the assaying of 
gold and silver, and in the gold bullion assay. 
It should be tested for silver. (See page 174). 

In the granulated form (when it is some¬ 
times called test lead) lead is as invaluable 
as borax glass for the scorification assay. It 
can be purchased of varying degrees of fine¬ 
ness and purity, or it can be made from bar 
lead by the assayer himself, as here directed. 

Melt pieces of the bar lead in any conven¬ 
ient vessel (odd sizes of sand crucibles, for 
instance), and when it is of a temperature 
just hot enough to char a splinter of wood, 
pour into a compactly-joined cigar box with¬ 
out a cover, or a strong starch box. I mine- 




T 5 2 


MANUAL OF ASS A TING. 


diately give a gentle rotary motion to the 
contents of the box, till the lead begins to 
thicken, and emits a slight creaking noise, 
when the motion is to be increased to a final 
vigorous shaking from side to side. A min¬ 
ute or two of this latter, and the thing is 
done. Sift through a 20-mesh or an ordinary 
flour sieve, and remelt that which remains on 
the sieve. When the entire batch has been 
thus granulated, assay for silver, following 
the directions on page 172. 

/y. Litharge (plumbic mon-oxide, yellow 
oxide of lead).—Employed mainly for the 
crucible assays of gold and silver ores. It 
should be dry, and free from any considera¬ 
ble amount of red oxide of lead, as this 
causes oxidation of silver, and consequently 
loss. Mitchell says: “ Ordinary litharge can 
be easily freed from this oxide by fusing it 
and pouring it into a cold ingot mould, then 
pulverizing, and carefully keeping it from 
contact with air, as it readily absorbs oxygen, 
and if it be allowed to cool in the atmos- 




RE AGENTS USED IN ASSA2UNG. 


*53 


phere, it will nearly all be converted into the 
red oxide.” 

Litharge can quite easily be procured free 
from large quantity of red oxide, and if it is 
kept in a tightly-stoppered bottle or tin can 
with closely fitting cover, there is little dan¬ 
ger of conversion to this oxide. 

It is used to furnish metallic lead that 
serves as a solvent for the precious metals in 
the ore. When in the melted state it has 
the power of giving up its oxygen to almost 
all the metals (save gold, silver and those of 
the platinum group), converting them into 
oxides, and since these are generally ex¬ 
tremely fusible, they go into the slag. Thus 
we are able to separate gold and silver from 
any baser metals they may be combined or 
associated with. 

Litharge is a very powerful desulphurizing 
agent (see Mitchell, pp. 181 to 187), and also 
serves as a metallic flux. 

It may safely be stated that all litharge 
contains silver to a greater or less degree. 



1 54 


MANUAL OF ASSAYING 


It may be, and generally is, in small quantity, 
but it is absolutely necessary to determine 
the amount, and to allow for it in the calcula¬ 
tion of silver in any ore tested. 

For the determination of this, see page 168. 

White lead (ceruse, plumbic carbonate, or 
carbonate of lead), and sugar of lead (plumbic 
acetate), can be made use of as substitutes 
for litharge, but they do not act quite so well. 

75. Iron .—A good desulphurizing agent, 
and as such is much employed in the assay of 
galena or sulphide of lead. Wire of inch 
diameter, and eight-penny nails are the cor¬ 
rect sizes. Iron filings can sometimes be 
used. 

16. Silver .—Can be bought as very thin 
foil. It is quite often needed in inquartation 
(which see). It should be tested for gold by 
dissolving \ gramme in pure nitric acid. After 
the solution is complete, there should be no 
black specks (gold), no matter how small, in 
the liquid. There is generally no difficulty in 
procuring silver perfectly free from gold. 






RE AGENTS USED IN ASSAYING. I 55 

77. Sulphur. — Ordinary commercial sul¬ 
phur. It is the sulphurizing agent. Used in 
Aaron’s crucible method to form mattes. 

(Oxide of iron and iron pyrites may be 
wanted for the assay of refractory copper 
ores—they need no especial description.) 

WET RE-AGENTS FOR ASSAYING. 

/. Distilled Water .—A most satisfactory, 
simple and efficient device for making it is 
the “Domestic Water Still,” made in two 
sizes, and costing $15.00, (^3 2s.) and $25.00, 
(^5 3 s -) respectively. Figs. 123 and 124 
give full and sectional views. To set up, 
screw the apparatus to a wall, over a sink. 
Attach a piece of rubber hose to the small 
faucet “ B,” at bottom and connect to faucet 
of water-pipe. The lower part of upper tube 
is the over-flow and should have a rubber 
hose connected and leading to the sink. A 
third hose attached to corrugated end of 
burner under the still, supplies the gas. T. he 
thumb-screw at bottom of still affords entrance 
to the still for cleaning purposes. The dis- 








MANUAL OF ASS A TING. 



Fig. 123. Fig. 124. 

Pure rain water is a very fair substitute. 
The main point in any case, is to see that it 
contains no chlorine (indicating usually, 
chloride of sodium or common salt). Test 
the water for this element by acidulating a 
clear sample with pure nitric acid, and adding a 


tilled water drops from the spout “ Z.” Light 
and regulate water supply until the waste water 
runs tepid. 

































RE-AGENTS USED IN ASSA YING. 


l 57 


drop or two of nitrate of silver solution (made 
by dissolving one part of the dry nitrate of 
silver in twenty parts of distilled water). The 
water should remain perfectly clear, that is, 
theie should not be in it the slightest cloudi¬ 
ness or turbidity. If it does show this, reject, 
and prepare or secure a fresh supply. 

2. Nitric Acid (hydric nitrate).—Indispens¬ 
able for parting , i.e., the separation of silver 
and gold by dissolving out the former. It can 
be procured perfectly pure, but should always 
be tested for chlorine , in same manner as is 
distilled water. Should it contain this objec¬ 
tionable ingredient, it can be removed by 
adding one drop of nitrate of silver solution 
and letting the acid stand in the light till the 
purple-black precipitate of chloride of silver 
settles to the bottom of the bottle. Then add 
a second drop, and let remain undisturbed as 
before. Continue these successive single drop 
additions until finally the last drop ceases to 
form any precipitate or milkiness in the acid. 
Draw off the clear acid and keep tightly stop- 




MANUAL OF ASSAYING. 


158 

pered. There are two reasons why chlorine 
should not be found in the nitric acid. First, 
it will tend to throw down, as silver chloride, 
the silver dissolved out of a bead by the 
nitric acid in the process of parting. Secondly, 
it indicates the presence of hydrochloric acid, 
and this acid forms aqua regia with the nitric 
acid, which could easily dissolve the very 
small amounts of gold sometimes left after 
parting. 

RE-AGENTS FOR ANALYSIS. 

The other re-agents, wet and dry, used in 
the qualitative tests, analyses, and special pro¬ 
cesses, are the following : 

Acetic Acid .— Needed in qualitative tests. 
Should be pure. Dilute with two parts dis¬ 
tilled water. 

Alcohol .— Wanted in the copper analysis 
and perhaps as fuel for a lamp. Use either 
common alcohol or wood spirits. 

Ammonia Water (ammonic hydrate, caustic 
ammonia, aqua ammonia).— If very strong, 






RE-AGENTS USED IN ASSA YING. 


T 59 


dilute one part with two parts of distilled 
water. 

Bi-chromate of Potash (potassic di-chro- 
mate).—Used in the volumetric determination 
of iron. Should be procured pure. 

Black Oxide of Manganese (manganese di¬ 
oxide).—Necessary to aid in the preparation 
of chlorine gas. Does not need to be per¬ 
fectly pure. 

Bromine. —Used to remove manganese from 
its solution, by precipitation, in the volumetric 
copper analysis. Agitate some of the liquid 
bromine with distilled water in a glass-stop¬ 
pered bottle, and use the resulting aqueous 
solution for the precipitation. 

Carbonate of Ammonium (ammonic carbon¬ 
ate, carbonate of ammonia).—Needed in the 
volumetric copper analysis. Should be pro¬ 
cured chemically pure. 

Carbonate of Sodium (sodic carbonate, car¬ 
bonate of soda). — Used in the volumetric cop¬ 
per and other analyses, to precipitate iron, 
manganese, blow-pipe test for manganese, etc. 






I DO 


MANUAL OF ASSAYING. 


Should be pure. Dissolve in ten parts dis¬ 
tilled water. 

Caustic Potash (potassic hydrate).— One 
part of common stick potash, dissolved in ten 
parts of water. 

Caustic Soda (sodic hydrate). — In stick 
form. Dissolve in distilled water — four 
parts — when wanted. 

Chloride of Barium (baric chloride, muri¬ 
ate of baryta).— One part of the pure salt 
dissolved in ten parts of distilled water. 

Chloride of Calcium (calcic chloride).—The 
dry, fused lumps, used to keep moisture away 
from fine scales. Need not be chemically pure. 

Citrate of Ammonium (ammonic citrate).— 
Dissolve one part of the salt in ten parts of 
distilled water. 

Citric Acid. — Pure, for volumetric copper 
and other analyses — to keep iron in solution. 

Cyanide of Potassucm (potassic cyanide, 
cyanide or prusside of potash).—Pure, for the 
volumetric copper analysis. 

Ferrocyanide of Potassiitm (potassic ferrocy- 










RE-AGENTS USED IN ASSAYING. 


161 


anide, yellow prussiate of potash).—One part 
of the pure salt, dissolved in twelve parts of 
distilled water. 

Hydrochloric Acid (muriatic acid).—To be 
pure. One bottle may be of the concentrated, 
a second of a mixture of one part acid with 
four parts of distilled water. 

Hyposulphite of Sodium (sodic hyposulphite 
or thiosulphate).—The pure salt is employed 
for the volumetric determination of mangan¬ 
ese, the chlorination test for silver, and as a 
precipitant for copper in the volumetric 
analyses of the ores of this metal. 

Iodide of Potassium (potassic iodide, iodide 
of potash).—Wanted in the volumetric deter¬ 
mination of manganese and as a test re-agent 
for lead. When used for the latter purpose, it 
may be either in the solid form, or in solution 
in water — one part in ten. 

Lime Water (calcic hydroxide).— Place a 
very little slaked lime in a bottle ; fill with 
water and shake. Keep tightly corked, and, 
when wanted, draw off the clear liquid with¬ 
out disturbing the sediment. 








MANUAL OF ASSAYING. 


1 62 

Mercuric Chloride (corrosive sublimate).— 
Needed only for the volumetric determination 
of iron, which see. 

Metallic Copper. — Wire for battery pur¬ 
poses, sheet for amalgamation test in panning, 
and some pure to form test solutions in the 
volumetric copper analysis, will be needed. 

Metallic Iron. —Pure, to precipitate copper 
from its solution, in the volumetric analysis 
of the latter metal. 

Metallic Merctiry (quicksilver).—Some that 
is impure can be employed to amalgamate the 
zinc plates of a battery, and some free from 
gold and silver will be wanted in the various 
amalgamation tests. 

Metallic Zinc. —In plates, forming a part of 
a battery. As a re-agent, zinc in pencils, or 
granulated, will be needed pure. 

Nitrate of Silver (argentic nitrate, lunar 
caustic).— See testing of distilled water for 
chlorine. 

Nitric Acid. —A bottle of pure and concen¬ 
trated acid, and one of the common commer- 





RE-AGENTS USED IN ASSAYING. 163 

cial (concentrated) for battery, should be on 
hand. 

Stannous Chloride (proto-chloride of tin, 
“tin salts”).— For the volumetric determina¬ 
tion of iron. 

Sulphate of Iron (ferrous sulphate, green 
vitriol, copperas).— In solution in water (of 
no particular strength) it is used to precipi¬ 
tate gold from its solution as a chloride, after 
the chlorination assay. 

Sulphate of Magnesium (magnesic sulphate, 
sulphate of magnesia, “ Epsom salts ”).— In a 
pure state, to precipitate arseniates in the volu¬ 
metric copper analysis, as a test re-agent for 
phosphates, etc. 

Sulphide of Iron (ferrous sulphide, sulphuret 
of iron).— See next paragraph but one. Can 
be purchased, or made by holding roll sulphur 
against a bar of red-hot iron. 

Sulp ho cyanide of Potasszzim (potassic sul- 
phocyanide).—One part of the pure salt dis¬ 
solved in ten parts of distilled water. 

Sulphuretted Hydrogen Water (hydrogen 





164 


MANUAL OF ASS A YING. 


sulphide gas dissolved in water).—Very use¬ 
ful in qualitative analysis. To generate it, fit 
together a simple piece of apparatus similar 
to fig. 125. The larger bottle, which may be 
of any capacity above six ounces, is provided 
with a doubly-perforated cork, through one 
hole of which passes a straight glass tube to 
nearly the bottom of the bottle, and terminat¬ 
ing in a funnel. Through the other hole a 
second tube passes a little way into the larger 
bottle, and bending twice at right angles, goes 
through the cork of the smaller bottle to 
nearly its bottom. A third tube leaves this 
smaller bottle and connects by a bit of rub¬ 
ber tubing with a fourth tube dipping into 
the receiving bottle containing distilled water. 
Place an ounce or two of sulphide of iron 
broken in small pieces in the bottom of the 
large bottle and fill half way up with ordi¬ 
nary water. The small bottle is to be half- 
filled with distilled water to wash the gas. 
Pour some common sulphuric acid into the 
funnel-tube, when the gas will at once be 





RE-AGENTS USED IN ASSAYING. 165 


given off. To ascertain when the water in 

# 

the re-agent bottle is saturated, hold the 
thumb tightly over its mouth, and shake. On 
releasing the pressure a little the thumb will 
be held down if the water is not saturated, 
but will be forced up, if the contrary is true. 

A little glycerine put in the re-agent bottle 
will help to retain the gas in solution. 



Sulphuric Acid (oil of vitriol).—A bottle of 
pure and another of common, both concen¬ 
trated. If dilute acid is wanted, mix, in a 
beaker, one part of the acid with five of dis¬ 
tilled water. 

Tartaric Acid .— Used to retain iron, 



















MANUAL OF ASSAYING. 


166 

alumina, etc., in solution, in the volumetric 

% 

copper analysis and in qualitative analyses. 
The pure salt can easily be procured. 

MISCELLANEOUS. 

Bone-ash .—For making cupels, which see. 
It is best to use a good quality. 

Chalk and Chalk Wash .— Ordinary chalk, 
to be used dry, and the same finely ground 
and rubbed up with water, for coating cru¬ 
cibles, etc. 

Clay Lute .— Fire-clay and sand, with solu¬ 
tion of common borax in water to bind them 
together. Horse and cow-hair may also be 
mixed with them. 

Riiddle (ferric sesqui-oxide, red oxide of 
iron, hematite).—A lump for marking cupels 
and scorifiers, and a paint (prepared by put¬ 
ting an ounce or two of the fine powder with 
water in a bottle, and shaking) for marking 
crucibles, coating frying-pan, etc., are wanted. 






CHAPTER III. 


TESTING OF RE-AGENTS. 

Before proceeding to make the regular 
assays, the student will find it expedient to 
examine his re-agents, either to ascertain the 
presence or absence of silver (and in the for¬ 
mer case, to determine its quantity), or to 
learn their various strengths, as shown in 
their reducing or oxidizing powers. 

The following five divisions include all the 
requisite tests of re-agents : 

I. Testing of Litharge for Silver. 

II. Testing of Granulated Lead for Sil¬ 
ver. 

III. Testing of Sheet Lead for Silver. 

IV. Determination of the Reducing Pow¬ 

ers of Reducing Agents. 

V. Determination of the Oxidizing Pow¬ 
er of Nitre (Nitrate of Potash). 

167 


\ 


MANUAL OF ASSA YING. 


168 


I. TESTING OF LITHARGE FOR SILVER. 

As stated in the chapter on re-agents, 
almost all litharge contains silver, generally 
as a small amount. However minute this 
may be, we must know exactly what it is, and 
allow for it in calculating the value of an ore. 

This we do by the crucible process, in the 
same manner as we should run an ore. (See 
Part II, Chapter I.) 

Mix very thoroughly the particular lot of 
litharge to be examined, and sample as usual. 

Make the charge 

* Assay ton Gramme Grain 

•weights. weights. weights. 

Bi-carb. soda. H A. T. 15 grammes.. 240 grains = y 2 oz. 

Carb. potash. % . 7V2 “ .. 120 “ = 14 “ 

Litharge. 1% “ 45 “ .. 720 “ = iV£ “ 

Charcoal, [ Any 1 gramme ... J 4 gramme. . 7*4 “ 

Flour, -j one of [ 1 “ 1 “ . . 15 “ 

Argol, L these, j 2 grammes... 2 grammes.. 30 “ 

Salt cover. 

Any one of the above charges will produce 
a lead button of from 15 to 20 grammes (131 to 
308 grains). 

Mix everything well, and brush into an “ S ” 

* See Chapter I, pp. 66-70,for full explanation of these weights. 











TESTING OF RE-AGENTS. 


169 


Battersea crucible or its equivalent (4! inches 
by 4^- wide). 

Have the fire quite hot, and heat crucible 
till contents are in quiet fusion, which will be 
in from twenty-five to thirty-five minutes. 
Take out, let cool, break, and hammer button 
into shape. 

If the button is too large for any cupel, re¬ 
duce by scorifying, then cupel. (See “ Scori- 
fication and Cupellation,” Part II, Chapter I.) 

Weigh the resulting silver button, and de¬ 
duct its weight from the gold and silver bead 
obtained from any crucible assay where the 
same quantity of litharge has been employed. 
If more or less than A. T. (or its equiva¬ 
lent in grammes or grains) is used, calculate 
and deduct accordingly. 

For example, one lot of litharge I have 
tested carried 0.75 (f) of a milligramme for 
the A. T., which amount was made the 
factor for that particular lot. 

The above amount, equivalent to \ ounce 
per ton of 2,000 pounds, is of course very 



I7O MANUAL OF ASSAYING. 

small, and, in the calculation of the value of 
an ore running say 100 oz. and upward, need 
not be deducted from the weight of the silver 
bead, since the loss of silver by absorption 
and volatilization from such a bead while 
cupelling, would more than counterbalance it. 
But it is very important that it should be 
deducted in the case of a poor ore, and 
especially when there is a question as to the 
presence or absence of silver in any ore. 

For the sake of practice, it will be well for 
the student to perform this crucible assay of 
litharge three or four times. 

Many assayers, and particularly those newly 
entered into the profession, continually try to 
obtain litharge (and for that matter, granu¬ 
lated lead) free from silver, meaning that it 
shall contain absolutely no silver. But, in the 
first place, they cannot procure it, and, in the 
second place, if they could, there would be 
nothing gained, in my opinion, by using such, 
as I will endeavor to show. 

First, in assaying ores which might be rich 



TESTING OF RE-A GENTS. \Jl 

in either gold or silver, it would make no dif¬ 
ference whether the litharge employed con¬ 
tained absolutely no silver, or the small 
amount it usually carries, for in the latter case 
its weight would not be deducted from that 
of the button for reasons just given. Sec¬ 
ondly, in ores very low in gold, it becomes 
very difficult, and sometimes impossible, to 
find the minute speck of gold left from the 
assay (particularly as the result of a scorifica- 
tion assay), even with the aid of the magnify¬ 
ing glass ; but when the litharge does contain 
a little silver, the latter not only leaves itself 
and the gold together in a visible and tangible 
form on the cupel, but it also serves to collect 
the gold during the process of crucible fusion, 
and retains it always thereafter. Thirdly, a 
small but known amount of silver in litharge, 
tests the assayer, his methods and practice, 
the litharge itself and some of the ores worked 
upon, for he ought to get the constant figure 
of the silver in the litharge when testing the 




I 7 2 MANUA L OF A SSA YWG. 

many worthless ores he is bound to examine 
in the course of his work. 

II. TESTING OF GRANULATED LEAD FOR SILVER. 

As in the case of'litharge, all granulated 
lead must have its amount of silver deter¬ 
mined, which is done by the scorification 
process. 

Mix and sample as usual. Rub the interior 
of the scorifier with a little fine silica before 
pouring into it any of the lead ; it will serve 
to protect the scorifier from corrosion by the 
molten lead. Weigh very carefully 2 A. T., 
60 grammes or 960 grains (2 oz.), of the lead, 
and pour into a 2f inch scorifier, and deposit 
on the top a piece of borax glass about the 
size of the head of a pin. 

Scorify and cupel as shown in the next 
chapter, and weigh resulting bead. The 
weight of the silver bead, divided by two, will 
give the number of milligrammes or fractions, 
that one assay ton (30 grammes, 480 grains, 
or 1 ounce) of the lead contains, which I 




TESTING OF RE-AGENTS. 


have found to vary from T 3 ¥ milligramme to 
i.2 milligrammes. 

Make a table of the amounts of silver con¬ 
tained in fractions and multiples of one assay 
ton, and post it in some convenient place for 
reference. I give an example of one particu¬ 
lar lot : 

0.50 A. T. contains 0.40 milligramme silver. 


0.80 


1.00 


u 



a 


1.20 

I.60 


a 


If other weights of lead are used, calculate 
accordingly. 

Deduct silver, in proportion due to the 
amount of lead used, from beads coming from 
ores ranging less than 100 ounces; above that 
disregard it, as with litharge. As with litharge, 
make several runnings of the lot of lead. 

The reasons given for desiring a litharge 
with some little amount of silver present are 
almost equally applicable to granulated lead. 



T 74 


MANUAL OF ASSAYING. 


IIT. TESTING OF SHEET LEAD FOR SILVER. 

Sheet lead can generally be purchased re¬ 
markably free from silver, and as it is seldom 
that a piece of more than ten or twelve 
grammes (120 to 150 grains) in weight is re¬ 
quired, the quantity of silver such a piece will 
contain will be exceedingly small. Moreover, 
its chief use being to enwrap gold and silver 
beads for recupellation, this amount of added 
silver is too minute to counterbalance the loss 
of silver by volatilization and absorption. 
Sheet lead is sometimes employed to aid in 
cupelling gold beads that have been in- 
quarted, and here a loss or addition of silver 
is not important. 

But should the lead-foil be suspected of 
carrying any quantity of silver, its exact 
amount can be determined by cutting off from 
various parts of the foil, and in small shreds, 
two or four assay tons (60 or 120 grammes, 
2 or 4 ounces), which are to be scorified and 
cupelled as usual. 




TESTING OF RE-AGENTS. 


175 


IV. DETERMINATION OF THE REDUCING POWERS 
OF REDUCING AGENTS. 

/. Argol (p. 146).—Weigh out the follow¬ 
ing charge: 

Bi-carbonate of soda.. 15 grammes, 240 grains ( £ oz.) 
Carbonate of potash.. 7-^ “ 120 “ ( J- “ ) 


Litharge.45 “ 720 “ (i£ “ ) 

Argol. 2 “ 30 


Salt cover. 

Put into a small crucible (size “ V ” of Bat¬ 
tersea), place in a hot fire, cover, remove 
when thoroughly fused, cool, detach button 
from slag, weigh, following the directions 
given for the crucible assays of gold and 
silver. 

The result, divided by two or thirty, will 
give the number of parts of metallic lead that 
one part of argol is able to reduce from 
litharge. It ranges around 8.5 parts. 

2. Cream of Tartar , or bi-tartrate of potash 
(p. 146). — Same charge as above, excepting 
that the two grammes or thirty grains of argol 
are to be replaced by three grammes or forty- 








176 MANUAL OF ASSAYING. 

five grains of the tartar. One part of pure 
tartaric acid will reduce 6 parts of lead, and 
the same amount of ordinary cream of tartar 
will reduce 6.4 parts of lead. 

3. Charcoal (p. 148).— Make up this charge : 
Bi-carb. of soda. .2 A. T., 60 grms., 960 grains or 2 oz. 
Carb. of potash ..} “ 7J “ 120' “ “ 4 “ 


Litharge.2 “ 60 “ 960 “ “ 2 " 

Charcoal.1 gramme or 15 grains. 


Salt cover. 

Use an “ S” crucible. As previously stated, 
the reducing power of one part of charcoal 
varies between 22 and 32 parts of lead. 

The reducing powers of the other sub¬ 
stances given on page 147 are determined in a 
similar manner to the three quoted above, 
running coals and coke as for charcoal, white 
sugar as for cream of tartar, flours, starches, 
etc., as for argol, etc. 

V. DETERMINATION OF THE OXIDIZING POWER 
OF NITRE (NITRATE OF POTASH). 

Determine the oxidizing power of the fine, 
dry salt (p. 148) by the following charge : 





TESTING OF RE-AGENTS. 


1 77 


Bi-carb. of soda.. 2 A. T., 60 grms., 960 grains or 2 oz. 
Carb. of potash . .J “ 7|- “ 120 “ “ p “ 


Litharge.2 “ 60 “ 960 “ “ 2 “ 

Charcoal.1 gramme or 15 grains. 

Nitre.5 grammes or 75 grains. 


Salt cover. 

Use an “S” crucible, and treat as in the 
previous crucible operations. The difference 
between the weight of the lead button ob¬ 
tained and that found in the assay of the 
charcoal, divided by five or seventy-five, will 
give the oxidizing power of the nitre, per 
part. It is about four parts. 






















































































PART II. 


ASSAYING. 












4 - 




























PART II. 


ASSAYING. 

CHAPTER I. 

GOLD AND SILVER ORES. 

Occurrence. —Gold is found in large quan¬ 
tities in the native state, designated by the 
various names of free gold, flour, leaf, wire 
and nugget gold. The minerals which most 
frequently carry gold are oxide of iron, pyrites 
of iron and copper (known as auriferous sul- 
phurets), arsenopyrite, and tellurium ores; of 
these, the most abundant are the first two. 

Minerals which less frequently are gold- 
bearing, are galena, blende, gray copper and 
“ carbonate ores.” 




182 


MANUAL OF ASSA YING. 


For a classification of silver ores I quote 
from Kustel’s “ Roasting of Gold and Silver 
Ores ”: 

“IMPORTANT SILVER ORES. 

The most important silver ores are those 
found in such quantities as to be an object of 
metallurgical operations. The principal min¬ 
erals of this kind are the following : 

A. Silver ores with unvariable amount of 
silver. — a. Sulphuret op silver , or silver 
glance, with 87 per cent of silver. It is of 
common occurrence. b. Brittle silver ore 
(stephanite ), or sulphuret of silver and anti¬ 
mony. This mineral contains 68 per cent of 
silver, and is quite common, c. Polybasite, 
sulphuret of silver, antimony and some ar¬ 
senic, with 75 per cent of silver, d. Ruby 
silver. The dark red silver ore, or antimonial 
variety, with 59 per cent, and the light red 
silver ore, or arsenical variety, with 65 per 
cent of silver, are valuable minerals. e. 
Miargyrite, sulphuret of silver and antimony; 
36.5 per cent of silver, f. Horn silver , or 




GOLD AND SILVER ORES. 


183 

chloride of silver, with 75 per cent of silver. 
g Iodic and bromic silver of yellow and green 
colors. 

B. Argentiferous ores with variable amount 
of silver. — a. Stromeyerite , or silver copper 
glance, a sulphuret of silver and copper con¬ 
taining up to 53 per cent of silver, b. Stete- 
feldite, with 25 per cent of silver, is an oxide 
ore. c. Silverfahlore , argentiferous gray cop¬ 
per ore. It contains silver in very variable 
proportions up to 31 per cent. This ore is 
quite common, and for this reason is impor¬ 
tant. It is also one of the most rebellious 
ores, containing copper, antimony, arsenic, 
sulphur, lead, iron, zinc, and sometimes gold 
and quicksilver, d. Chloride ores (so-called), 
mostly decomposed ores, generally of an 
earthy appearance and different colors. They 
contain more or less finely divided chloride of 
silver. 

C. — a. Argentiferous lead ores , galena, or 
sulphuret of lead, lead glance. Generally, this 
is not rich in silver, containing from $20 to 




184 


MANUAL OF ASSAYING . 


$60 per ton. Specimens assay sometimes as 
high as $300.* b. Cerussite , carbonate of 
lead. If pure, without admixture of copper 
and other carbonates, it is poor in silver in 
most cases, c. Argentiferous zinc blende , sul- 
phuret of zinc. Pure zinc blende contains 
usually only traces of silver ; often, however, 
it assays well, even up to $400 per ton. d. 
Argentiferous pyrites . Copper and iron py¬ 
rites are poor in silver, but often auriferous. 

There are, besides, numerous classes of 
decomposed silver ores, generally of earthy 
nature ; also, half decomposed ores which 
have lost their metallic glance, having a black 
or bluish-black color, and being generally 
cupriferous.” f 

Assay. —We can best consider the system¬ 
atic fire treatment of gold and silver ores, by 
dividing it into a series of operations, and 
taking each in turn and in detail. 

* I have found them as high as $1,500 per ton. (W. L. B.) 

f See appendix for extended lists of the minerals of or contain- 
ing gold and silver. 



GOLD AND SILVER ORES. 


185 

The three main divisions are : 

I. Preparation of the sample. 

II. Scorification process. 

III. Crucible process. 

\ 

I. PREPARATION OF THE SAMPLE. 

The first thi nof to be done in the treatment 
of an ore, whether it is to be assayed for gold, 
silver, copper, lead, or any other metal, is to 
place it, that is, to label it. This is best ac¬ 
complished by giving to it a running number, 
never to be repeated. By adopting this sys¬ 
tem of numbering all samples, any danger of 
confusing specimens from various mines or 
parts of the same mine or vein, is entirely 
gotten rid of. Have a notebook at hand, 
and, in it, under the number, write such items 
as may be necessary or useful, as the date 
when sample was received, name of person 
sending it, character of the ore, nature of the 
charge, weights employed, calculations, etc. 
To pieces of the ore which are to remain 
whole, affix gummed labels, bearing the same 



186 


MANUAL OF ASSAY INC. 


number. To preserve the final pulverized 
samples, bottles of about four ounces capacity, 
cork-stoppered, and similarly labelled, can be 
employed, or what is even better, pasteboard 
boxes in size about 5^- inches long by 3 i 
inches wide and 2 inches high, will be found 
to be very serviceable. They can be written 
on, thus requiring no labels. 

The next step is to secure an average sample 
for assay, and its importance cannot be over¬ 
rated. An ore is by no means of uniform 
character, being, in general, made up of the 
gangue or valueless portion of the ore, through 
which are scattered the valuable minerals. 
Therefore, unless the sample finally chosen 
for assay represents an average of the entire 
lot, being a mixture in the same proportions, 
of the richest, the medium and the poorest 
portions, as in the original ore, the assay itself 
is worthless, no matter how carefully it may 
have been performed.* 

* In this connection, I would refer the student to an article 
“On the Commercial Sampling of Minerals,” by Mr. L. S. Austin, 
of Salt Lake City, Utah, which appeared in the “ Engineering and 
Mining Journal” (July 22, Aug. 5, Aug. 26, and Sept. 16, 1882). 



GOLD AND SILVER ORES. 


187 


To illustrate the averaging, take a quantity 
of ore weighing fifty pounds, which may be as 
a single lump, or, better, the result of the 
selection of samples across a section of the 
vein. In' order to get a fair average, it is not 
necessary to operate on a larger quantity than 
this amount, for above it, should come in, as 
a more practical test, the mill-run. 

With a heavy sledge-hammer, break up the 
entire mass into pieces of about the size of a 
hickory-nut. Should the rocks be so large or 
so very hard as to obdurately resist the ham¬ 
mer, they may be brought into submission by 
that process called “astonishing,” by Prof. 
Chapman, in his valuable little work. It con¬ 
sists in heating red-hot the resisting pieces, 
and plunging them while thus into some cold 
water in a pan. This heroic treatment will 
either at once reduce the lump to small 
pieces, or render it so friable that light pound¬ 
ing will pulverize it. Pour off the water and 
dry the contents thoroughly, then break into 
small pieces as directed. Transfer to a large 





t 88 


MANUAL OF ASSAYING. 


sheet of heavy brown or manilla paper, then, 
with a large iron or steel spatula, thoroughly 
mix, by turning over and over and by stirring 
in together with the dust, the finer and coarser 
particles, till satisfied that the whole is a 
homogeneous mixture. 

(At this stage of the operation it is a good 
plan to reserve a characteristic lump or a few 
pieces, from an examination of which the 
nature of the ore may be determined, and 
process of treatment decided upon.) 

Now divide in halves by means of a very 
large spatula or piece of heavy sheet brass, 18 
inches long by 4 inches wide, and -|~inch thick. 
Break up still finer (to the size of a hazel-nut 
or less) the half selected. Mix again and 
halve as before. Continue the crushing, mix¬ 
ing and halving until about one pound has 
finally been sampled down. 



Fig. 126. 

















GOLD AND SILVER ORES. 


189 


Instead of halving, the piles may be quar¬ 
tered, and two of the diagonally opposite 
quarters taken as a half. Fig. 126 shows the 
pile entire, divided, quartered, and two of the 
quarters removed; parts 1 and 4, or 2 and 3, 
are to be put together. 

When the ore to be assayed is less than 
fifty pounds, ranging down to a pound or two, 
it can be broken still smaller in the successive 
steps, and when it is but a few ounces in 
weight, the whole of it should be crushed and 
pulverized, as directed. Wet or damp ores 
and pulps should be dried before pulverizing. 

The student must exercise his judgment in 
a measure, with regard to the sampling of an 
ore, simply remembering that the object, as 
before stated, is to obtain a final product 
which shall be an exact counterpart, in rela¬ 
tive proportions, of the metals and gangue of 
the original ore. 

Instead of halving, the broken ore may be 
taken up on a sampling shovel, and thrown 
on a tin or copper sampler, making it a rule 




190 MANUAL OF ASSAYING. 

to reject either all that which goes between 
the prongs or ribs, or that which remains up¬ 
on them. These two articles are convenient, 
but not necessary. 

The third step is to pulverize the sample 
finally obtained, which may be done very sim¬ 
ply though somewhat laboriously (depending 
considerably upon the nature of the ore), by 
means of an iron mortar and pestle. A towel 
wrapped loosely around the pestle and across 
the top of the mortar will prevent loss due to 
flying particles. 

Sift through a sieve of eighty or ninety or 
even of one hundred meshes, since the finer 
the powder, the more quickly will it be acted 
upon in the furnace. Ores which contain 
much clay or lime are very apt to clog the 
meshes of the sieve so that little will pass 
through. This may generally be obviated by 
placing in the sieve an ounce weight or equal¬ 
ly heavy piece of smooth iron, the movement 
of which in shaking keeps the meshes open. 
Do the sifting over a piece of brown paper, 



GOLD AND SILVER ORES. I 9 I 

■ s 

and be sure that all the sample passes 
through the sieve, for the few minute parti¬ 
cles or scales, that might remain on the sieve 
and be hastily thrown away, could be of suffi¬ 
cient value to vitiate the assay. I might give 
here, however, a little suggestion made me by 
Mr. H. H. Corbin, of Telluride, Colo. Cer¬ 
tain ores contain free silver (with a little gold 
in it, sometimes), to such an extent that while 
they will not produce many scales, yet there 
may be a few left on the sieve. In such cases 
dump the scales on the grinding plate and 
cover them with the finely-powdered ore which 
has already gone through the sieve. Grind 
heavily for quite a little while, then sieve 
again. It will be found that most of the 
scales have been ground by the ore (particu¬ 
larly when the latter is quartzose), fine 
enough to go through a ioo-mesh sieve. If 
they will not, repeat the treatment until they 
will. Three grindings will usually suffice. 
The sievings are to be very carefully mixed. 
Even all this trouble is less than that of the 



192 


MANUAL OF ASSA YING. 


ordinary scale method of treating ores con¬ 
taining the precious metals in the free state. 
(See in appendix, “ Assaying of Ores con¬ 
taining Free Gold or Free Silver”.) 

Mix again the fine powder, and with a large 
brush transfer to the properly marked box or 
bottle, when the sample is ready for assay. 
Do not shake the box or bottle between the 
times of grinding and weighing, as this tends 
to cause the gold, silver, sulphurets, or other 
heavy minerals to settle, resulting in an un¬ 
equal distribution of the various constitu¬ 
ents of the ore. If much time elapses be¬ 
tween the weighings and the second treat¬ 
ment the ore should be remixed. 

When very many assays have to be per¬ 
formed daily, the rubbing-plate and rubbers 
will be found so very convenient and so time- 
and-labor-saving, that they will become almost 
necessities. (See pp. 29-32 for description.) 

The operation of grinding, or rubbing, or 
pulverizing, is managed as follows : The ore, 
previously broken into fine pieces as directed, 



GOLD AND SILVER ORES. 


193 


is placed upon the clean surface of the plate, 
the rocker is now laid upon it, and with one 
hand firmly pressed upon the body of the 
rocker, and the other grasping its handle, it is 
moved backward and forward with an oscil¬ 
lating motion. This knack of grinding, al¬ 
though not easy to describe, is soon acquired. 

After grinding, the plate should be thor¬ 
oughly cleaned, which can be done by rubbing 
on it either sand, quartz, broken glass, com¬ 
mon salt, old cupels or scorifiers, broken cru¬ 
cibles, the slags from scorifications, or some 
worthless ore, finishing with an old rag. Very 
great pains should be taken to perfectly clean 
the plate after grinding much free gold ore or 
such rich ores as tellurides. 

In place of the sheets of brown paper al¬ 
ready mentioned, and which quickly become 
full of holes, the zinc sifting-pans (p. 41, fig. 
18) ora rubber cloth, can be used to advantage. 

To guard against loss of dust, the tin box- 
sieve (p. 40) is recommended. There is an¬ 
other laboratory plan for systematic sampling, 




194 


MANUAL OF ASSAYING. 


which is very fair, though slow and best suited 
for small lots of from 5 to 20 pounds of 
ore. For this the assayer needs four sieves 
in addition to the fine one—they are 2, 4, 8 
and 16-mesh, respectively. 

Crush the sample so that it will just about 
go through the 2-mesh sieve, mix thoroughly, 
divide in halves, reject one-half, and crush 
the remainder so it will just pass through the 
4-mesh sieve. Again mix, divide in halves, 
reject half, and crush the other half for the 
8-mesh sieve. Mix, halve, reject half, and 
crush for the 16-mesh sieve. The half kept 
from this is all to be pulverized and put 
through the 100-mesh. All this insures 
thorough mixing and uniform crushing and 
sampling. 

Having now finely ground the ore to be 
assayed, we must next decide how to treat it. 

There are two methods of assaying gold 
and silver ores, the scorification and the cru¬ 
cible. 

The process to be chosen depends chiefly 




GOLD AND SILVER ORES. 


*95 


on the nature of the ore. In general, we may 
say the scorification process is better adapted 
for all silver ores, and for rich gold ores (in¬ 
cluding telluride ores of any degree of rich¬ 
ness). 

The crucible process serves better for low 
grade gold ores. The advantage of this pro¬ 
cess lies mainly in the fact that it enables us 
to operate upon a larger quantity of ore; oth¬ 
erwise it is no better than the scorification 
method and indeed in many respects the lat¬ 
ter is to be preferred. 

The scorification process is so much simpler 
to use, easier to comprehend, and so satis¬ 
factory in its working, that I shall give it the 
first place in this manual. 

II. SCORIFICATION PROCESS. 

The object of this process is to so act upon 
an ore with heat, access of air, and certain 
re-agents, that the precious metals shall be 
driven out of their combinations with the 
impurities of the ore (or if free, separated 



196 


MANUAL OF ASSAYING. 


from them), and be retained alloyed with 
another metal, lead, and from which they can 
afterwards be separated. 

The chief re-agents are lead, in a granu¬ 
lated condition, and borax glass. 

Besides these, silica, iron, and bi-carbonate 
of soda are occasionally employed. 

The ore, mixed with the lead, and covered 
with the borax glass or other flux, is put into 
a scorifier and subjected to heat in a muffle. 

Under the action of the heat, the lead 
melts, and being scattered throughout the 
ore, seizes upon the gold and silver and set¬ 
tles with them to the bottom of the scorifier. 
The borax glass or other flux attacks the 
gangue and impurities present, and uniting 
with them and with litharge resulting from 
oxidation of some of the lead, forms a slag or 
glass, which floats upon the surface of the 
molten lead. 

So much for the theory of scorification; in 
practice we follow in regular rotation the 
steps here given: 




GOLD AND SILVER ORES. igj 

a. Preparation of Charge (including weigh¬ 
ing of ore, roasting, weighing of re-agents, 
mixing, etc.) 

b. Scorification. 

c. Cupellation. 

d. Weighing the Gold and Silver Bead. 

e. Parting. 

f. Inquartation. 

g. Weighing the Gold Residue. 

h . Calculations. 

a. Preparatio 7 i of Charge. 

Whatever subsequent treatment (including 
roasting) an ore is to undergo, the amount 
required for assay must always be weighed 
first. If the ore is in a box, it can be sampled 
therein, but it is better to pour from it or from 
the sample bottle onto a clean piece of black 
glazed paper or sheet rubber, and with a 

spatula form it into a smooth 
square. Divide into smaller 
squares with a rule and take 
a dip from each division, as 
shown in sketch. 



Fig. 127. 
















MANUAL OF ASSAYING. 


I98 

Have ready cleaned a number of the scori- 
fiers. Number or letter each scorifier with 
ruddle (liquid or lump), weigh the requisite 
amount of granulated lead, divide approxi¬ 
mately in halves, and transfer one-half to the 
scorifier. Upon it brush the ore (roasted or 
not) and mix by means of a small steel spatula. 
Pour the remaining half of the lead evenly 
over the surface of the mixed ore and lead, 
and over all sprinkle the borax glass. In simi¬ 
lar manner prepare all the other charges. 

A deviation from this method has been fol¬ 
lowed by some assayers. Their procedure is 
to put, say, \ of the lead at the bottom of the 
scorifier, then the ore and \ of the lead mixed 
previously, topping all with the remaining { of 
the lead. This change is due to the fear of 
unacted-upon ore remaining at the bottom of 
the scorifier. I am inclined to consider it an 
almost unnecessary refinement. 

In many assaying establishments, notably 
the larger ones, the practice of marking scori- 
fiers, cupels, and crucibles does not obtain. 






GOLD AND SILVER ORES. 


1 99 


Instead of this, a systematic order of arrang¬ 
ing these articles is kept up, either in or out of 
the furnace, and this routine of position and 
order of working is never varied, so that by 
relative place a sample can always be identi¬ 
fied. This plan is indeed a good one, and 
perhaps imperative where very much work is 
done, but for the beginner, for a time at least, 
the custom of marking everything had better 
be adopted. 

CHARGES. 

(For manner of roasting see “ III. Crucible Process.”) 

i. One for “every day” ores, serving well 
for the common run of ores in which the 
metals are not in excess of the gauge, is the 


following: 

Ore. £ A. T., 5 grammes, 96 grains or £ oz. 

Granulated lead. “ 45 “ 7 2 ° “ 

Borax glass.250 mgrms., or 4 grains. 


Use it for ores that do not contain much 
copper or lead. 

2. Copper glance or copper pyrites : 

Ore . ^ A. T., 2^ grammes, 48 grains or T V oz. 

Granulated lead 2^ “ 75 “ 1,200 “ 2 i 

Borax glass .200 mgrms., or 3 grains. 







200 


MANUAL OF ASSAYING. 


For the above ores, a preliminary roasting 
can be made, if considered advisable. 

If not to be roasted, and when there is not 
very much of the sulphurets present, heat 
gently for a time, till the roasting in the scori- 
fier is done. 

If rich in sulphurets, a strong heat can be 
applied at once, melting everything down into 
a sort of matte, then proceeding as usual. 

3. Copper matte: 

Matte . T \j A. T., 2^ grammes, 48 grains or r ' 7 oz. 

Granulated lead ....3 “ 90 “ 1,440 “ 3 “ 

Use no borax glass ; instead : 


Powdered silica.A. T., i| grammes, 24 grains or ^ oz. 

4. Gray copper ores : 

Ore.xV A. T„ 2\ grammes, 48 grains or ^ oz. 

Granulated lead.2 “ 60 “ 960 “ 2 “ 

Borax glass..300 mgrms., or 5 grains. 

5. Sulphurets of iron : 

Ore. \ A. T., 7i grammes, 120 grains or \ oz. 

Granulated lead.2 \ “ 75 “ 1,200 “ 2±> “ 

Borax glass. 200 mgrms., or 3 grains. 


Litharge can be used to advantage in this 
as in other unroasted sulphurets. 













GOLD AND SILVER ORES. 


201 


Always weigh the litharge, so as to allow 
for its contained silver. 

6. Oxide of iron : 


Ore .A. T., 5 grammes, 96 grains or £ oz. 

Granulated lead.1^ “ 45 “ 720 “ “ 

Silica. 1 “or 15! “ 

Borax glass.350 mgrms., or 5^ grains. 


The silica to be mixed with the charge—it 
can be diminished as the percentage of silica 
in the ore increases. 

7. Galena: 


Ore . \ A. T. t 15 grammes, 240 grains or ^ oz. 

Granulated lead.1^ “ 45 “ 7 2 ° “ “ 

Borax glass.100 mgrms., or i| grains. 


Gentle heat. A nail in the scorifier aids in 
the desulphurization. 

8. “ Carbonate ” ores : 


Ore. . A- T., 5 grammes, 96 grains or } oz 

Granulated lead. 2 “ 60 “ 960 “ 2 

Borax glass. \ gramme or 7% grains. 

9 “ Chloride ” ores : 

Ore. | A. T., 5 grammes, 96 grains or \ oz. 

Granulated lead.1^ “ 33 “ 57 & “ *5 

Borax glass. 3 °° mgrms., or 5 grains. 


Use as low a heat as possible until the 



















202 


MANUAL OF ASSAYING. 


charge has covered over, then heat more 
strongly to complete fusion, 

io. Blende : 


Ore .| A. T., 5 grammes, 96 grains or £ oz. 

Granulated lead .3 “ 90 “ i, 44 ° “ 3 

Borax glass.400 mgrms., or 6 grains. 


Needs a good heat and care in its assay. 

11. Arsenical and antimonial ores : 


Ore..£ A. T., 5 grammes, 96 grains or £ oz. 

Granulated lead.4 “ 120 “ 1,920 “ 4 

Borax glass.i| grammes or 23 grains. 


This charge may have to be divided — 
sometimes requires several re-scorifications. 
A piece of charcoal laid over the scorifier, or 
some of it pulverized and dropped therein, 
often aids the fusion, as has been previously 
remarked. 

12. Tellurides : 


Ore.A. T., z\ grammes, 48 grains or T \y oz. 

Granulated lead.2 “ 60 “ 960 “ 2 “ 

Litharge.j 1 ^ “ 2| “ 48 “ 

Borax glass.250 mgrms., or 4 grains. 


Sprinkle the litharge over the mixed 
charge. The buttons may need repeated 
scorifications with plenty of lead (20 to 1). 















GOLD AND SILVER ORES. 


203 


13. Native gold or silver, or very rich ores 


of any kind : 

Ore.Y 1 ^ A. T., grammes, 48 grains or oz. 

Granulated lead._i| “ 45 “ 720 “ “ 

Borax glass..250 mgrms., or 4 grains. 


Ores, either those already described or any 
others, having a great quantity of lime or 
baryta, will require more borax glass than the 
quantities given. It may need to be as much 
as the ore taken — in such cases the charge 
may have to be divided, and several scorifica- 
tions and re-scorifications made. Such large 
quantities of borax are best added at inter¬ 
vals, not at the beginning. Stirring will often 
aid. Give a strong heat. Make use of silica 
also. 

The weights of borax glass are put down 
more to serve as indications than for precise¬ 
ness’ sake. It need not be weighed at all ; 
after a time the assayer will learn to use it in 
pinches. 

Study and experiment are necessary here. 
Ores will be found made up of several of 
those given separately above —new combina- 










204 


MANUAL OF ASSAYING. 


tions of minerals are constantly coming to 
light. 

The operator must then work over the par¬ 
ticular ores he comes in contact with, until he 
learns them thoroughly. 

The colors shown by the interiors of scori- 
fiers are often characteristic of the ores 
tested, and in conjunction with the colors of 
the cupels after cupellation make valuable 
tests. The following descriptions may per¬ 
haps be of some value to the student in this 
connection : 


COPPER. 

Scorifier (See color plate).—A green, more 
or less deep, according to the percentage of 
this metal. Where the coating is somewhat 
thick, as on the edges of the scorifier, the 
color becomes a dark brown, but the prevail¬ 
ing tint is green. 

Cupel.— Slate green, ranging to blackish 
green — prevailing tint very dark blackish 
green. There is frequently a rose coat on the 



SCORIFIER 

COLORS. 




U R A N I U M. 


CHROMIUM. 












GOLD AND SILVER ORES. 


205 


outside of cupels from ores rich in copper, 
which need not be mistaken for the rose color 
of oxide of silver. This rose tint meeting the 
slate green produces a purplish black or purp¬ 
lish green. 

IRON. 

Scorifier (See color plate).— With large 
amounts of iron the interior is black with a 
gray metallic lustre (this indicates a poor 
fusion), from which the color ranges down 
through a deep rich mahogany and varying 
shades of red-brown to a light yellow-brown. 
A red-brown is, however, always present, and 
is the prevailing color. 

Cupel .— A brown tint, more or less decided. 

LEAD. 

Scorifier (See color plate).—Various shades 
of lemon yellow. 

(Vanadium, cadmium, and bismuth give 
same shades.) 

Cupel .— Bright, rich yellow to lighter 
shades. 




206 


MANUAL OF ASSAYING. 


(Small amounts of antimony, arsenic, bis¬ 
muth, cadmium or zinc retained in the button 
also leave yellow markings on the cupel.) 

MANGANESE. 

Scorifier (See color plate).—From a purple- 
black to a light violet-brown or amethyst 
color. 

Cupel .— Blackish green to a lighter green, 
usually the latter. It is never so deep nor 
the cupel so thoroughly permeated by the 
color as is the case with copper ; the color 
also is different. 

CHROMIUM. 

Scorifier (See color plate).— Blood-red — 
thicker portions of the glaze a green, but pre¬ 
vailing tint is an orange or blood red. 

Cupel. —Lemon-yellow, with reddish edges, 
surface also somewhat mottled with reddish- 
brown blotches — characteristic appearance. 

NICKEL. 

Scorifier .— A dirty, brownish yellow, and 
not very characteristic. A lead ore with a 
little iron would imitate it exactly. 








GOLD AND SILVER ORES. 


207 


Cupel. —Brown, almost identical with iron. 

URANIUM. 

Scorifier (See color plate).—A peculiar red. 

Cupel. —Brown, as for iron. 

COBALT. 

Scorifier. — A beautiful blue ; toward the 
bottom it struggles with a green, which is 
probably due to the union of the yellow oxide 
of lead and the cobalt blue. This color will 
not be obtained from any ore, but it is proba¬ 
ble that it has its effect in modifying other 
colors. 

Cupel. —Brown, as for iron. 

TELLURIUM. 

Scorifier .—A yellowish color, with some red 
spots ; not very characteristic. 

Cupel. —Yellow, with small green stains. 

It must be borne in mind that combinations 
of the metals are liable to influence these col¬ 
ors and to produce mixed shades. 

Also both the scorifier and cupel must be 
examined, not one alone, for the scorifier may 





208 


MANUAL OF ASS A YING. 


reveal one metal, the cupel another. Thus 
an ore containing about equal parts of copper 
and iron gives a red-brown in the scorifier, in¬ 
dicating iron, while the green of the copper is 
almost entirely masked. On the other hand, 
the cupel is green-black, indicating copper, 
while no brown of the iron is visible; hence 
both tests prove both metals to be present in 
the original ore. 
b. Scorification. 

Place the scorifiers, by means of the scori¬ 
fier tongs (page ioo, fig. 50) in the middle and 
back of the muffle, which should be decidedly 
hot , close the door and augment the draft. 

Then begins the first operation, the melting 
or fusion of the lead, due to intense heat and 
absence of oxygen, which takes from three to 
four minutes. 

When the lead is liquid, open the door, thus 
admitting a current of air to supply oxygen, 
and which will also tend to diminish the heat 
somewhat. 

Now, in the case of ores containing or re- 




GOLD AND SILVER ORES. 


209 


taining antimony, arsenic, sulphur, or zinc, a 
second operation, roasting, begins and con¬ 
tinues till the greater proportion of the sub¬ 
stances named have volatilized, the remainder 
of them going into the slag. 

D uring this time the borax glass has melted 
and begun uniting with the gangue of the ore 
and with oxide of lead to form a slag which 
surrounds as a ring the molten lead. 

As the scorification goes on, the melted 
lead grows smaller and smaller by oxidation 
and the volatilization of the greater part of 
the oxide formed, while the ring of slag grad¬ 
ually closes in and finally covers the lead, 
which is seen no more. 

Finally increase the heat for a minute or 
two to fully liquefy the slag, which will finish 
the process of scorification. 

Remove the scorifiers, and pour their con¬ 
tents into the cups of the scorification moulds 
(page 105, figs. 60 to 63), which should not be 
cold, covering each receptacle with its proper 
scorifier to retain its identification. (If neccs- 



2 IO 


MANUAL OF ASSA YING. 


sary, these scorifiers can be again employed 
for ores, etc.) 

After having poured the charge, it will be 
well to let the slag and button remain in the 
cavity of the mould until they are stone cold 
before dumping them out, as otherwise there 
is danger of the lead adhering firmly to the 
slag. 

Instead of pouring, the leads can be allowed 
to cool in their scorifiers, but no advantage is 
gained by this, and they take a longer time to 
cool. 

In either case, however, when cold, detach 
the lead buttons from their slags, and hammer 
each button into a clean cube with fiat- 
IM M tened corners (fig. 128). Were the 
fig- 1 28 -corners to be left sharp, they would 
injure the cupel when the button came to be 
dropped into it. 


The weight of the button will vary accord¬ 
ing to the conditions ; the nature of the ore, 
the size of the charge, the heat of the furnace 
and the length of time the charge was allowed 





GOLD AND SILVER ORES. 


2 I 1 


to remain in it, all exert an influence. A good 
weight is from twelve to sixteen grammes, 
which will make a cube of about one-half inch. 

The button of lead is to be marked with 
some identifying number or letter with the 
point of a file or knife-blade. 

The button should be perfectly malleable ; 
if brittle it has probably retained antimony, 
arsenic, zinc or litharge, which can be gotten 
rid of by re-scorification. But with ores very 
rich in gold proceed with care, for the brittle¬ 
ness may be due to the gold itself, as beyond 
a certain limit gold takes away from the 
malleability of lead. If the button is large no 
extra lead need be added ; if small an assay 
ton or two may be melted with it. 

Again, the button may be very hard on ham¬ 
mering or show red in places, and perhaps on 
taking out of the scorification mould may 
have mossy copper on the bottom. In such 
cases the button must be re-scorified until no 
more copper is seen, or until it is very malle- 




2 I 2 


MANUAL OF ASSAYING. 


able. Plenty of lead must be used to alloy 
with the copper. 

Since there is a greater loss of silver by 
cupellation than in scorification, very large 
buttons should be scorified down to a size 
suited to the cupels. 

Examine the slag, and if it contains any 
globules of lead, hammer them flat, then place 
them on top of the main button, and cupel all 
together. 

The slag should be vitreous or glassy, and 
of uniform character, its color depending upon 
the nature of the ore. 

The scorifier should be perfectly smooth in 
its interior, that is, it should have no semi- 
fused lumps adhering thereto. Occasionally 
it may be corroded or eaten away, which does 
not necessarily injure the assay, unless the 
corrosion extends through the dish and allows 
its contents to flow out upon the floor of the 
muffle. In such a case (when of course the 
assay must be repeated) at once cover the 
floor of the muffle with dry sand or bone-ash, 




GOLD AND SILVER ORES. 


213 


using the muffle shovel (fig. 58), and scrape 
out the mass adhering to it by means of the 
hoe or scraper (fig. 64). If this cleaning 
out of the muffle after an accident by spilling 
or leakage is not attended to, it leads to 
either one or both of two evils : first, the 
melted lead and borax attack the muffle and 
rapidly eat a hole through it; secondly, they 
stick to any scorifier or cupel placed in the 
muffle, making it almost impossible to move 
or remove either without breakage or loss of 
contents. 

The corrosion of the scorifier is a good hint 
to add silica to similar ores, for usually it is 
the lack of this in the ore that causes the 
abstraction of silica from the scorifier, though 
there are times when a mixture of much lead 
and little ore is being scorified, that the lith¬ 
arge formed by the oxidation of the lead itself 
attacks the scorifier, and again, as in case of 
compounds rich in copper (a copper matte, for 
instance), the oxide of copper attacks the 
scorifier. 



214 MANUAL OF ASSAYING. 

Sometimes in the process of scorification a 
crust forms over the surface of the charge 
and refuses to break. Such a crust is gener¬ 
ally due to arsenical and antimonial ores pres¬ 
ent, and may often be destroyed by dropping 
in the scorifier some powdered charcoal 
wrapped in a wad of thin paper. 

The oxidation can also be commenced by 
stirring the charge with a bent wire, until the 
lead is uncovered and begins to act. Withdraw 
the wire, break off the mixture adhering to the 
end and return it (the slag, etc.) to the scori¬ 
fier, as it will probably carry some of the ore. 
c. Cupcllation. 

This operation consists in oxidizing the 
lead of the lead buttons, the litharge formed 
by the heat being partly absorbed by the 
cupel and partly driven up the chimney, leav¬ 
ing the gold and silver together as a bead 
upon the surface of the cupel. Other metals 
that may have remained in small quantity 
from the previous operations, are also oxi¬ 
dized and so gotten rid of. 




GOLD AND SILVER ORES. 215 

Take a good cupel (pages 114-117, fig. 79), 
in weight about one-third greater than that of 
the button that is to go in it, blow out any 
dust or impurities from the interior, mark on 
its sides in three or four places with ruddle or 
the point of a file, its appropriate number or 
letter, and with the aid of the cupel tongs or 
cupel shovel and hoe, place it in the muffle and 
there let it remain some four or five minutes 
that it may acquire the temperature of the 
furnace. 

As can be inferred from the preceding 
paragraph, the size of the cupel depends 
upon the size of the lead button. And as 
mentioned under cupel-making, it is a good 
plan to have on hand cupels of various 
weights. It is stated that a good cupel will 
absorb its own weight of litharge, and further¬ 
more, it is able to take a button heavier than 
its own weight, for a large amount of litharge 
(or oxide of lead) is driven off in fumes and 
consequently does not enter into the body of 
the cupel. But it is better to employ a cupel 




MANUAL OF ASSAYING. 


2 16 

the weight of which is from one-fourth to one- 
third more than that of the button, for when 
a cupel becomes nearly saturated with litharge, 
the cupellation proceeds too slowly, when, on 
the contrary, it ought to be somewhat 
hastened, and cases occur that the cupellation 
ceases, though there may be at the bottom of 
the cupel enough unattacked bone-ash to 
absorb the remaining lead. 

At other times an assayer may carelessly 
put altogether too large a button in a cupel, 
and therefore all the bone-ash in the cupel be 
saturated with litharge while there is yet 
melted lead above. This error may some¬ 
times be rectified by putting a second cupel, 
red hot and inverted, under the soaked cupel, 
when the cupellation will proceed, though 
slowly. But it is better to reduce by scorifi- 
cation,- in the first place, the excessively large 
button. 

When the cupel or cupels have been in the 
muffie a few minutes, and consequently have 
become of the same temperature as the inte- 




GOLD AND SILVER ORES. 21 J 

rior of the muffle, the lead button or buttons 
are to be placed in them, each one in its 
proper cupel, by means of the smaller curved 
tongs (page ioo, fig. 48), and the muffle-door 
of the furnace closed, having previously, if 
necessary, placed a couple of pieces of coke 
or charcoal in the mouth of the muffle. 

If the muffle has been of the proper tem¬ 
perature, in a minute’s time or less, all the 
lead buttons will have quietly fused, and, on 
opening the muffle-door, each will be seen as 
a little lake of molten metal, from which arise 
fumes of oxide of lead. 

The closing of the door at first is simply in 
order to melt the lead buttons, by the in¬ 
creased heat and absence of air. 

It is very difficult to give in words direc¬ 
tions for the proper conducting of this impor¬ 
tant step of cupellation. Experience is the 
best instructor. 

In general, do not have the furnace too hot. 
This is not a matter of so much importance 
in the cupellation of the lead buttons from 



MANUAL OF ASSAYING. 


2 l8 

eold ores, but in those from rich silver ores it 
is such. 

“ The heat is too great when the cupels are 
whitish, and the metallic matter they contain 
can scarcely be seen, and when the fume is 
scarcely visible and rises rapidly to the arch 
of the muffle” (Mitchell), and par tutelar ly 
when the melted lead bubbles. 

“ The heat is not strong enough when the 
smoke is thick and heavy, falling in the muffle, 
and when the litharge can be seen not liquid 
enough to be absorbed, forming lumps and 
scales ” (Mitchell), hi short, to speak seem¬ 
ingly paradoxically, when the muffle and con¬ 
tents look cold. 

An extremely high heat is bad, but a low 
heat is worse. “ When the degree of heat is 
suitable the cupel is red, and the fused metal 
very luminous and clear” (Mitchell), and 
when scales of litharge are found in small 
quantity around the inner circumference of the 
cupel; in short, this “feathering” shows that 
the fire has not been too hot. 



GOLD AND SILVER ORES. 2 I 9 

All this time, however, the buttons have 
been growing smaller and smaller, by oxida¬ 
tion and by volatilization and absorption of 
the oxide, changing from flat liquids to con¬ 
vex ones, and this reduction continues until 
we reach the point when the last of the lead 
leaves the bead. This is known as the 
“ brightening,” “flashing,” “ blicking,” “cor¬ 
uscation,” or “ figuration. ” As the button of 
gold, silver, and lead arrives near this stage it 
appears to revolve with great velocity, and 
rainbow colors succeed each other all over its 
surface. Finally a film passes over the bead, 
and then no more action is visible. 

(With poor silver ores and ordinary gold 
ores the final bead is so small that it is diffi¬ 
cult, if not impossible, to see the “blicking,” 
but on beads from silver ores of any richness 
the brightening shows well that the operation 
of cupellation is concluded.) 

Now move the cupel to the hottest place in 
the muffle, or increase the heat by closing the 
muffle door, that the last traces of lead may 





220 


MANUAL OF A SSA YING. 


be driven off. One source of error in silver 
assays is due to the assayer not getting rid of 
all his lead from the beads, but instead he 
weighs and reports it as silver. Better err by 
under-reporting rather than over, so take the 
chances of volatilizing a little .silver from the 
bead than to allow lead to remain with the 
silver. A minute is generally sufficient to 
drive off the last lead, but with ores contain¬ 
ing more gold than silver, let the cupel remain 
in the hot part three or four minutes, for 
there is no danger of losing any gold in that 
time. 

Very rich ores betray themselves by a pe¬ 
culiar mottled appearance of the molten lead 
shortly after the cupellation begins. The 
luminous blotches of litharge as they form 
string themselves out and cover the lead as 
with a network. This is very characteristic, 
and once seen is again easily recognized. 
This mottling appears also with almost any 
buttons a little before the blicking ; in short, 
the richer the button the sooner it is observed. 



GOLD AND SILVER ORES. 


22 I 


Silver beads, on being suddenly brought 
from the hot interior of the muffle to the 
front where it is cooler, or out into the open 
air, sometimes “ spit ” or “ blossom ”— that is, 
the bead sprouts or vegetates, forming foliated 
protuberances all over its surface. This may 
occasion loss, as the spitting throws off parti¬ 
cles of the silver; hence, guard against this as 
much as possible by moving the cupel by de¬ 
grees to the front, and when at the mouth of 
the muffle cover with an inverted hot cupel. 
With beads weighing less than 30 milligrammes 
or thereabouts this need not be done, but above 
that weight proceed carefully. 

If the assayer is running a number of as¬ 
says, let him so arrange the cupels that those 
intended for buttons from poor silver ores or 
o-old ores shall be in the center or hottest part 

o 1 

of the muffle, while those for rich silver ores 
shall be in the fore part or cooler section. 
The reason for so doing is this: silver is sensi¬ 
bly volatile at a high heat, and the higher the 
temperature the greater the loss. On the 





222 


MANUAL OF ASSA Y/A T G. 


other hand, the smaller the percentage of sil¬ 
ver in a silver-lead, the less loss of this metal. 
By therefore placing the rich silver-lead in the 
cooler portions, the tendency is to decrease the 
loss by volatilization. With any furnace, the 
heat of which cannot be instantly controlled, 
the muffle often becomes a little too hot for 
perfect cupellation. When but few cupels are 
therein this does not matter much, since they 
can be slid to the front; but it is of impor¬ 
tance when the muffle is so well filled that it 
becomes difficult or impossible to move any 
particular cupel or group of cupels to a cooler 
spot. By now putting in the muffle a small 
cold scorifier or cupel, letting it rest on the 
edges of four of the cupels, the interior can 
be cooled down considerably. Several scori- 
fiers or cupels thus arranged have quite a low¬ 
ering effect on the temperature, at least for a 
time. 

When many cupels are being managed at 
once make a chart of their relative positions 
in the muffle, that there may be no “ cases of 



GOLD AND SILVER ORES. 


223 


mistaken identity ” afterward, for with large 
buttons in small cupels the litharge often ob¬ 
literates the ruddle marks. 

If the furnace is too cold cupellation ceases, 
and the lead button is said to “freeze,” form¬ 
ing a bunchy mass which undergoes no fur¬ 
ther action. A piece of charcoal laid upon 
the cupel, and additional heat applied, will 
sometimes finish the cupellation, or the but¬ 
ton may be dug out of the old cupel, wrapped 
in a piece of lead-foil, and be re-cupelled in a 
new cupel. The result either way is none too 
accurate. 

The final silver and gold bead from any 
cupellation should adhere with some tenacity 
to the cupel, have a bright, rounded surface, 
and appear frosted below. 

d. Weighing the Gold and Silver Bead. 

When cold detach the bead from its cupel, 
using the point of a knife-blade, and keeping 
a finger on the bead while so doing if the 
bead be small, for otherwise the exertion put 



224 


MANUAL OF ASSAYING. 


forth to loosen the bead might easily snap it 
out of the cupel and past finding. 

Lift the bead from the cupel by means of 
delicate pincers (p. 126), and cleanse from any 
adhering cupel dirt by rolling in the palm, by 
using a small stiff brush, or, if necessary, by 
flattening a little by means of a small steel 
hammer and anvil. If the bead be very small, 
fold it in three or four thicknesses of tissue 
paper, to prevent its flying away under the 
strokes of the hammer. 

Weigh on the bullion scales in milli¬ 
grammes and fractions. 
e. Parting. 

The separation of gold and silver by dis¬ 
solving out the latter is designated by the 
term “parting.” 

The bead after weighing is flattened a little 
if it has not been so treated before. Now 
place in a little clean porcelain capsule or cru¬ 
cible (fig. 85), and fill about a quarter full 
with water (free from chlorine, see p. 156), 
and add four to six drops of concentrated 



GOLD AND SILVER ORES. 


225 


nitric acid. No exact rule as to the amount 
of acid to add can be given, nor indeed is it 
necessary. But in general add drop by drop 
till it begins to “bite” the bead — that is, when 
the latter seems in violent motion and bub¬ 
bles are thrown rapidly off. Instead of add¬ 
ing concentrated acid to water containing the 
bead, until it takes hold of the latter, the 
assayer may use a diluted acid of known 
strength. 16 parts of nitric acid of 41 0 Beau me 
(specific gravity 1.41) with 30 parts of dis¬ 
tilled water will make an acid of 21 0 Beau me 
(specific gravity 1.16). This will do for ordi¬ 
nary small beads; for large ones, after having 

• 

treated them with the above 1.16 acid, add 
some of 32 0 Beaume (specific gravity 1.26), 
made by mixing 16 parts of the strong 41 0 
acid with 10 parts of distilled water. Make 
these up in quantity and preserve in well 
stoppered bottles. 

Now place the capsule on a sand-bath or 
wire triangle, and heat gently, not enough to 
cause the acid solution to boil. After a time 






226 


MANUAL OF ASSAYING. 


no more action goes on. If there is no gold 
in the bead it will not blacken on adding the 
acid, and nothing will remain undissolved in 
the capsule; it will contain only the clear solu¬ 
tion of nitrate of silver, formed by the silver 
dissolving in the acid. 

In this case nothing further need be done 
than to wash out the contents of the capsule 
into a bottle containing silver residues. 

But should one or more black specks be 
seen at the bottom of the capsule or float¬ 
ing about in the liquid, gold may or may not 
be present; at all events, these specks, how¬ 
ever small , must be treated as though they 
were gold. Pour off the liquid above the 
black particles, first lightly tapping the cap¬ 
sule in order to cause the floating gold to 
settle to the bottom. If tapping will not 
either settle the gold or bring the particles 
together, try “churning” — that is, stir the 
contents of the capsule vigorously with a 
glass rod. In many cases, and unless the gold 
is in too fine a state, this will coagulate the 



GOLD AND SILVER ORES. 


227 


gold, as it were — that is, bring the particles 
together into a spongy mass — when tapping 
will quickly settle it. It is best to pour into 
another clean porcelain dish, so that should 
the gold, by some mischance, go over with the 
outpouring solution, it may be recovered. Fill 
up the capsule with water, care being taken 
that no speck of gold is blown out of the cap¬ 
sule by the jet of water from the wash-bottle. 
This is to wash out the nitrate of silver from 
the gold. Tap the gold to the bottom, pour 
off the washings, and repeat the washing. If 
there is much gold, a third washing may be 
necessary. All this to insure complete re¬ 
moval of the silver nitrate. Finally drain off, 
wipe the capsule dry, remove, by means of 
filter paper (or clean blotting paper), any 
drops of water adhering to the interior of the 
capsule (being careful not to take away any 
of the gold), and heat very gently at first till 
all moisture has been driven off, then intensely 
for a minute or two. The gold has now 
changed in color from black to its normal yel- 






228 


MANUAL OF ASSAYING. 


low, and is very nearly pure, enough so for all 
practical purposes. Let the capsule and con¬ 
tents cool. 
f Inquartation . 

When a bead of gold and silver contains 
the gold in a greater proportion than about 
one-third of the silver, it possesses the power 
of resisting the solvent action of nitric acid. 
A certain amount of the silver may dissolve, 
according to the relative proportions of the 
two metals, but the larger part of it will 
remain so enveloped by the gold, that the 
strongest acid will not attack it. 

Hence we resort to inquartation, or the 
operation’ of producing an alloy of gold and 
silver in such proportion that the latter metal 
may be extracted by nitric acid. 

By the color of the bead the assayer can 
judge whether it needs to undergo this opera¬ 
tion. If it be of a moderately yellow color or 
a brighter yellow, it will probably need it. But 
there can be no doubt of it if it refuses to be 
acted upon by the acid. 



GOLD AND SILVER ORES. 


229 


Remove it from the capsule, and dry. 
Weigh some thin and pure silver foil, in 
quantity about twice the weight of the bead. 
Wrap the latter in the foil, and place both in 
a cupel (or in a small hole bored in the back 
of the cupel), and fuse them well together in 
the dame of a blow-pipe. When cool, remove 
the now largely increased bead from the cupel, 
flatten and part as directed. 

Instead of employing the blow-pipe, the 
bead and silver can be enfolded in some sheet- 
lead, and be re-cupelled in the usual manner. 
Indeed, if the original bead weighs more than 
ten milligrammes, it will be easier to alloy it 
by cupellation than by blow-piping, and a 
much better fusion be obtained. 
g. Weighing the Gold Residue. 

By means of a pointed slip of wood or sharp 
knife-blade, transfer the gold (which should be 
one scale or film) to the scale-pan of the bull¬ 
ion balance, and weigh with exceeding care, as 
usual in milligrammes and fractions. It often 
happens that the minute black pin-point of 



2 30 


MANUAL OF ASSAYING. 


gold becomes too small to be weighed after 
the heating. It can then be reported only as 
a “ trace ” or “ color.” 
h. Calculatio 7 is. 

By the use of the system of assay ton 
weights, the calculation of the gold and silver 
value of an ore becomes very simple. Two 
examples will show this very clearly : , 

Example No. i. 

Amount of ore taken. -J- A. T. 

Amount of test-lead used. “ 

Mgkms. 

Weight of gold and silver bead. 8.50 

“ silver in A. T. lead.25 

True weight of gold and silver bead. 8.25 

Weight of gold in the bead. 1.10 

Weight of silver in the bead. 7.15 

7 -i 5 x 5 = 35-75 = 35? milligrammes = 35! 
ounces per ton of silver in the ore. 

1.10x5 = 5.5 = 5i milligrammes = 5^ ounces 
per ton of gold in the ore. 

VALUE OF THE ORE: 


Gold—5J ounces @ $20 67 per oz.$113.68 

Silver—35} “ “ 1.29 “ .. 46.11 

Total value per ton.S 1 59-79 
















GOLD AND SILVER ORES. 


231 


Example No. 2. 


Amount of ore taken 
Amount of test-lead used 



Mgrms. 


Weight of gold and silver bead. 

Weight of silver in test-lead*. 

True weight of gold and silver bead . 
Weight of gold, “faint trace”. 

Weigh of silver in the bead. 


231.9° 


231.90 


231.90 


0.00 


0.00 


231.9x 2=463.8=463^- milligrammes=463 T 8 ¥ 
ounces per ton of silver in the ore. 

Value : 463.8x$ I - 2 9 = $597-30 per ton. 


CRUCIBLE PROCESS. 


This process is much more complicated 
than the scorification, and, to use it success¬ 
fully, we should know pretty thoroughly the 
nature of the re-agents employed, the kind 
and degree of their re-actions upon each other 
and upon the ore while in the crucible sub¬ 
jected to heat, and, finally, the characters of 
the various ores and their modes of behavior 

* Not deducted. Read remarks on testing of granulated lead 
for silver, p. 173. 












232 


MANUAL OF A SSA YING. 


in the crucible. Knowing all these things, 
we can decide upon such a modification of 
treatment as is best adapted to the particular 
ore in question. 

The crucible process can be applied to any 
gold and silver ore, of whatever mineralogical 
nature, and whether rich or poor, but it has 
been found by experience to be best fitted for 
certain ores and classes, as is the scorification 
for certain others. 

By some assayers the crucible process is 
reserved almost entirely for low grade ores 
(whether in gold or silver), and the scorifica¬ 
tion for high grade ores , and, for a general 
rule, this will do very well. Another broad 
distinction is that of confining the crucible 
process to gold ores, and the scorification to 
ores of silver. This latter rule is quite a safe 
one to follow, since the majority of gold-bear¬ 
ing ore is low grade, and hence is best assayed 
by the crucible process, which operates upon 
a larger quantity than the scorification. Fur¬ 
ther, an ore of silver which is so poor as to 



GOLD AND SILVER ORES. 


233 


give no results by the scorification process, is 
practically worthless, and needs no more test¬ 
ing by any method. 

The following classification covers the 
ground, both generally and, in a measure, spe¬ 
cifically: 

CRUCIBLE PROCESS. 

1. Gold ores. 

2. Low grade gold ores.* 

3. Low grade silver ores. 

4. “Chloride ores” (sil¬ 

ver), including: 

Chlorides, 

Bromides, 

Chloro-bromides, 

Iodides. 


An outline of the 
follows : 

The ore is mixed with lead in some form, 

* For the purposes of assaying, a gold ore which runs over $5 
to the ton may be considered high grade ; below that figure, low 
grade. 


SCORIFICATION PROCESS. 

1. Silver ores. 

2. High grade silver ores, 

with the exception of 
the chloride and al¬ 
lied ores. 

3. High grade gold ores. 

4. Telluride ores. 

5. Arsenical and antimo- 

nial ores. 

6. Ores containing tin. 

7. Ores containing nickel 

or cobalt. 

crucible process is as 





234 


MANUAL OF ASS A YING. 


fluxes, with or without some reducing, oxidiz¬ 
ing, sulphurizing, or desulphurizing agent, 
transferred to a crucible and heated. The 
reduced lead absorbs the gold and silver, and 
settles with them to the bottom, while all im¬ 
purities are fluxed ( i.e ., slagged), matted, or 
volatilized. After removal from fire the lead 
is freed from slag, and the gold and silver 
separated from it by cupellation, as previously 
described. 

To elaborate the above description some¬ 
what, we may state, that, in the crucible pro¬ 
cess, as in the scorification, lead is added 
(save for lead ores) to extract the precious 
metals from the ore ; but, instead of using it 
in the metallic state and oxidizing the excess, 
we start with a compound which is almost in¬ 
variably the oxide, litharge, and by means of 
a reducing agent, or by the reducing action of 
the ore itself (or by both combined), reduce 
enough lead to retain all the gold and silver, 
but which amount of lead shall not be too 
large to be manageable. 






GOLD AMD SILVER ORES. 


235 


To secure a perfect crucible fusion, which 
means practically the separation of the gold 
and silver from everything else that may have 
been associated or combined with them in the 
ore (excepting, perhaps, some of the lead), 
we need to do several things. To get rid of 
the gangue (or earthy portion of the ore) we 
use fluxes, which convert the gangue into a 
slag. All metals present, save the precious 
ones, may be removed in various ways : By 
uniting them with sulphur into a matte ; by 
oxidizing them and fluxing the oxides into the 
slag ; by oxidizing them and volatilizing the 
oxides entirely out of the crucible ; or, in the 
one case of lead, by bringing either the whole, 
or such a proportion of it as may be wanted, 
down with that obtained from the litharge. 
Next, we may or may not need some reducing 
agent to reduce the requisite amount of lead ; 
or, on the contrary, an oxidizing agent may be 
necessary to oxidize and so remove sulphur or 
the excess of lead when an ore of this metal 
is being treated. Finally, a protecting cover 




236 


MANUAL OF ASSAYING. 


of some easily fused inert substance will be 
wanted, although it is not indispensable. 

The chief fluxes are litharge, the carbon- 
ates and bi-carbonates of potash and soda, 
borax, silica, and nitre. The reducing agents 
are charcoal, argol, cream of tartar, flour, or 
some other similarly carbonaceous substance, 
for it is the carbon of the reducing agent 
which removes the oxygen of the litharge, 
leaving metallic lead. The most commonly 
used oxidizing agent is nitre. Sulphur is the 
sulphurizing agent, and common salt the pro¬ 
tecting cover. (The chemical composition 
and reactions of all the above are mven in 

o 

detail in the chapter on re-agents, which see.) 

It will now be well, and in order, to under¬ 
take a little study of gold and silver ores, or 
of ores which are imagined to contain the 
precious metals, that we may know how to 
apply to them their proper treatment, which 
includes a knowledge of the principles of the 
important art of fluxing. 



GOLD AND SILVER ORES. 


237 


Every ore must belong in some one of the 
following divisions : 


Metalliferous min¬ 
eral or minerals 
with no gangue; 
examples, pure 
galena, iron py¬ 
rites, or any “con¬ 
centrates.” 


Metalliferous min¬ 
eral or minerals 
with a gangue; 
examples, galena 
or iron pyrites in 
quartz. 


Gangue matter with 
no perceptible met¬ 
alliferous mineral 
or minerals; ex¬ 
amples, quartz, 
fluor spar or ba¬ 
rytes. 


The third division can, of course, include 
specimens that actually contain no metallifer¬ 
ous minerals, perceptible or imperceptible, as, 
for example, pure white quartz, while in 

J 

others, as stated, they may be present so mi¬ 
nutely disseminated as to be invisible to the 
naked eye (or even to the eye assisted by a 
good magnifying glass), as is often true of 
samples carrying gold in that very fine condi¬ 
tion known as “dour gold.” 

There are also instances where that which 
is ordinarily a metalliferous mineral may act 
as a gangue ; for example, galena in spathic 
iron. Here the latter is a gangue, whereas 
at other times it may be found as a mineral 





238 


MANUAL OF ASSAYING. 


in a true gangue. No confusion, however, 
need arise, if we consider only the question 
of the composition of the particular sample 
lying before us. 

The chief value of the above classification 
lies in the fact that a knowledge of the class 
to which an ore belongs aids us in its fluxing. 

It would be almost impossible to write such 
descriptions as would enable the student to 
determine the mineralogical character of an 
ore or to place it in its proper division above. 
He must learn by experience, by observation, 
and by an application of the information im¬ 
parted by the standard authorities on miner¬ 
alogy and blow-pipe analysis which are listed 
in the appendix. The few simple qualitative 
tests given in the latter may aid him some¬ 
what. 

As regards the relative amounts of gangue 
and mineral in an ore, I can give but one gen¬ 
eral, and rather indefinite, line of advice : 
The heavier an ore, the greater the percent¬ 
age of metalliferous mineral; the lighter an 



GOLD AND SILVER ORES. 


239 


ore, the greater the percentage of gangue. 
There are a few exceptions to this rule ; the 
chief one commonly met with is barytes or 
heavy spar, a gangue which is three-fifths as 
heavy as galena, the chief ore of lead. 

If an ore to be treated belongs to the first 
division — that is, if it possesses no gangue — 
we supply an artificial one, as it were, when 
we come to prepare the charge, by adding 
silica. 

For purposes of assay treatment, we may 
consider under one heading those ores which 
appear to be all gangue, or made up of both 
gangue and mineral. 

The nature of the gangue is important in 
determining the nature of the flux necessary 
to change it all into a slag. The gangue may 
be acid , basic , or both acid and basic ; conse¬ 
quently, the simple rules for fluxing a gangue 
are almost self-evident. An acid gangue re¬ 
quires a basic flux; a basic gangue requires 
an acid flux . Now, what do we mean by an 
acid or a basic gangue ? An acid gangue is 




240 


MANUAL OF ASSAYING. 


simply one which acts as an acid, requiring a 
base to form a salt. A basic gangue, on the 
contrary, acts as a base, and therefore requires 
an acid to form a salt. As examples of these 
chemical facts, take metallic copper, which is 
a base. To convert it into a salt of copper 
we need an acid, which may be sulphuric, this 
making sulphate of copper (common blue 
vitriol), or silicic acid, forming silicate of cop¬ 
per (the mineral chrysocolla is the hydrated 
silicate of copper), or any other acids, form¬ 
ing corresponding salts. So in fluxing, an 
acid gangue, as silica, forms salts with a basic 
flux, as litharge or soda, producing a slag 
which is composed of the silicates of lead and 
soda, and a basic gangue, as lime, unites with 
acid fluxes, as silica or borax, producing a 
slag which is composed of the silicate and 
borate of lime. There results then the fol¬ 
lowing classification : 



GOLD AND SILVER ORES. 


24 I 


ACID GANGUES. 

1. Quartz, or other forms 

of uncombi?ied silica; 
as quartz crystals, 
quartz rock, quartz¬ 
ite, sandstone, sand, 
etc. 

2. Silicates, or silica com¬ 

bined with some base; 
as clay, clay slates, 
mica, etc. 

3. Rocks in which silica 

predominates; as gran¬ 
ites, feldspars, por¬ 
phyry, etc. 

As a rule, then, an acid 
gangue is silicious. 


BASIC GANGUES. 

1. Calc spar (carbonate of 

lime). Also lime- 
stones. 

2. Heavy spar (barytes, or 

sulphate of baryta). 

3. Fluor spar (fluoride of 

calcium). 

4. All so-called earths; as 

alumina, and various 
combinations of lime, 
magnesia, baryta, 
etc., without silica. 

5. Sparry iron, or carbon¬ 

ate of iron. 

6. Various metallic ox¬ 

ides; as those of iron, 
manganese, etc., 
when in sufficient 
quantity to be con¬ 
sidered as gangues. 


We can easily see now that the gangue of 
an ore may be both acid and basic, by its being 
made up of representatives of both classes. 
Theoretically, then, such a gangue should 




242 


MANUAL OF ASSA YING. 


flux itself. Practically, however, we may find 
it necessary to help the fusion a little. 

Try to ascertain the mineralogical character 
of the gangue. When this is known, con¬ 
sider only the element which is in excess of 
the others, and flux that ; the remaining ones 
will usually take care of themselves. 


ACID FLUXES. 

1. Borax. 

2. Silica. 

3. Silicates ; as glass, and 

silicate of lead or 
lead-glass formed by 
the fusion of litharge 
and silica. 

Hence these flux the 
basic gangues enumer¬ 
ated. 


BASIC FLUXES. 

1. Litharge. 

2. Nitre. 

3. Carbonate of soda. 
Carbonate of potash. 
Bicarbonate of soda. 
Bicarbonate of potash. 

Hence these flux the 
acid gangues enumer¬ 
ated. 


The metalliferous minerals of an ore play 
a very important part in its treatment. They 
may exert either one of two very opposing 
actions, viz.: reducing, that is, taking away 
oxygen (from the litharge), or oxidizing, that 
is, giving up oxygen (to the reducing agent). 




GOLD AND SILVER ORES. 


2 43 


To explain a little more fully: Sulphur, 
arsenic, antimony, and zinc are the principal 
reducing elements of an ore. (If an ore con¬ 
tains none of these, it will not be at all reduc¬ 
ing.) They all act in a similar manner to the 
carbon of a reducing agent, removing oxygen 
from the litharge, and so leaving metallic lead, 
themselves being converted into oxides. The 
various methods for eliminating these obnox¬ 
ious substances will be considered further 

An effect contrary to that produced by the 
elements mentioned is that caused by certain 
oxides and oxidized minerals. They are 
chiefly the oxides of iron, lead, copper, and 
manganese, in their highest forms of oxida¬ 
tion. Exposed to heat in a crucible, and sur¬ 
rounded by the reducing agent, they give up 
to it a portion of their oxygen, themselves 
being converted into their lower oxides and 
going into the slag. 

The presence, then, of either reducing or 
oxidizing elements in an ore is made manifest 





244 


MANUAL OF ASSAYING. 


by the size of the resulting lead button, the 
former tending to produce lead, the latter to 
keep it in the oxidized state by appropriating 
to themselves the carbon intended for reduc¬ 
ing. Thus, some ores will be more or less 
reducing, bringing down more lead than is 
wanted, just enough or too little, or they may 
reduce no lead at all. On the other hand, 
they may be oxidizing, not only not bringing 
down any lead, but preventing the reducing 
elements of the ore (if present) and the re¬ 
ducing agent added from exerting their action. 
Hence it is important to know what an ore’s 
action is. 

It is advisable to reduce a certain portion 
of the litharge in order to obtain a button of 
a convenient size for cupellation. It should 
be large enough to extract all the gold and 
silver from the ore, yet not be so large as to 
be too long time cupelling, which may cause 
a loss in silver. A standard weight is 15 
grammes for those who use the metric sys¬ 
tem, or 240 grains (£ ounce) for those accus- 



GOLD AND SILVER ORES. 


2 45 


tomed to the grain weights. If the buttons 
obtained should chance to be somewhat larger 
or smaller, it will make no material difference; 
but it is well to use either weight given, and 
calculate ores and oxidizing and reducing 
agents to such a basis. 

For the sake of reference, I next give lists 
of the principal ores and minerals whose direct 
or indirect action upon the litharge has just 
been discussed. 

Metalliferous minerals which have a reduc- 
dng action : 

SULPHURETS. 

1. Sulphuret of zinc (sphalerite, blende, zinc 

blende, “jack” or “black jack”). 

2. Sulphuret of manganese (manganblende, 

alabandite). 

3. Sulphuret of iron (pyrite, iron pyrites, 

mundic). 

4. Sulphuret of iron (pyrrhotite, magnetic 

iron pyrites). 

% 

5. Sulphuret of iron with arsenic (arsenopy- 

rite, mispickel, arsenical iron pyrites). 



246 


MANUAL OF ASSAYING. 

6. Sulphuret of copper (chalcocite, copper 

glance, vitreous copper). 

7. Sulphuret of copper and iron (chalcopy- 

rite, copper pyrites). 

8. Sulphuret of copper and iron (bornite, 

erubescite, variegated copper pyrites, 
“ horse-flesh ore ”). 

9. Sulphuret of copper and antimony with 

sulphurets of iron, zinc, silver, mercury, 
bismuth, arsenic, etc. (tetrahedrite, gray 
copper, fahlerz). 

10. Sulphuret of antimony (stibnite, gray an-* 

timony). 

11. Sulphuret of lead (galenite, galena, “py¬ 

rites of lead,” “mineral”). 

12. Sulphuret of silver (argentite, silver 

glance). 

The above list enumerates the chief sul¬ 
phurets which are likely to be assayed for 
gold and silver, though there are many other 
intermediate and mixed sulphurets, for de- 

0 

scriptions of which consult the mineralogies. 
It can easily be remembered, however, that 








GOLD AND SILVER ORES. 


247 


any sulphuret, or mixture of sulphurets, is 
reducing. 

To the above add the various arsenides, 
antimonides, bismuthides, selenides, etc., of 
more or less rarity, and more commonly ores 
containing graphite or plumbago. 

Metalliferous minerals which have an oxid¬ 
izing action : 

1. Red oxide of iron (“ decomposed iron 

»>\ 

ore ). 

2. Red oxide of lead (minium). 

3. Black oxide of copper (tenorite, melaco- 

nite). 

4. Black oxide of manganese (pyrolusite). 

(More rarely the chromates). 

Since an oxidized ore commonly results 
from the decomposition of a sulphuretted 
one, it may be very possible to find an ore 
not entirely decomposed or oxidized, and 
therefore both reducing and oxidizing. As 
examples, one often meets with a specimen 
carrying sulphurets and oxides of iron, or 



248 


MANUAL OF ASSA YING. 


copper pyrites and black oxide of copper in¬ 
termingled, or galena and carbonate of lead. 

A preliminary examination of an ore may 
then be necessary to determine its character 
and subsequent mode of treatment. An ex¬ 
pert mineralogist, metallurgist, miner, or as- 
sayer can tell almost at a single glance the 
nature of an ore as to its constituents and 
oxidizing or reducing powers, but the begin¬ 
ner will find it somewhat difficult at first. 
Here then again comes in the opportunity to 
make blow-pipe and qualitative examinations. 

To ascertain the presence or absence of 
sulphurets, try the following very simple test: 
Powder a little of the sample and heat it in 
an iron spoon over a strong flame or on top 
of a good fire, and note its behavior. If, 
shortly after it is heated, star-like sparks are 
quickly thrown off (particularly noticeable 
when the powder is stirred with a wire), then 
the mass begins to glow around the edges 
(resembling a charcoal fire), while closely 
above it hover small blue flames, and finally 



GOLD AND SILVER ORES. 


249 


the entire mass becomes red-hot, with fumes 
and an odor as of a burning match is per¬ 
ceived, then sulphurets of iron or copper or 
both are present, and so the ore will be decid¬ 
edly reducing. If, in addition, an onion or 
garlic-like odor and whitish fumes are noticed, 
arsenic (probably as arsenical iron pyrites) 
is also present. Antimony and zinc give white 
fumes with no odors. Blende and galena are 
not so liable to glow and to scintillate as are 
the iron and copper sulphurets, but the smell 
of a burning match should be perceptible upon 
heating them or any other ore which contains 
a fairly large percentage of sulphurets. It 
will also be noticed that after the mass has 
been thoroughly heated and allowed to cool, 
it will have lost its metallic shimmer, and be¬ 
come of a dull, dead color, indicating oxida¬ 
tion. 

A simple chemical test for sulphurets may 
easily and quickly be tried. Place a small 
portion of the finely ground ore in a test- 
tube, pour in a little water, shake, add a few 



250 


MANUAL OF ASSAYING. 


drops of hydrochloric acid, and warm gently. 
If the smell peculiar to rotten eggs (sulphu¬ 
retted hydrogen) is now recognizable, sulphu- 
rets are certainly in the ore. 

Finally, when it is suspected that not a very 
large quantity of any sulphuret is in the sam¬ 
ple, try the following plan, which is much more 
delicate than either of the preceding : Fuse a 
little of the ore with bicarbonate of soda and 
borax on charcoal, by means of the blow-pipe. 
When the mass has fused remove it, by means 
of a knife-blade, to the surface of a bright 
silver coin, add a drop of water, and work the 
paste thus formed for a short time. The same 
gas above spoken of (sulphuretted hydrogen) 
is given off from the sulphide of sodium, 
which has been made by the union of the sul¬ 
phur of the ore and the soda, and blackens 
or browns the coin, according to the amount 
of sulphur in the original ore. 

A very close guess as to the kind of sul¬ 
phuret contained in an ore, or of which it is 
mostly composed, can frequently be made (de- 



GOLD AMD SILVER ORES. 25 I 

pending on the purity of the sulphuret) by 
noting the color and character of the pulver¬ 
ized sample, then heating some quickly in a 
roasting dish, observing its action under heat, 
finally examining the heated ore, after it has 
cooled. Compare it with the following table : 



2^2 


MANUAL OF ASSAYING. 


Kind of Sulphuret. 


i. Blende 


Before Heating. 


Color of Ore. 


2. Manganblende .. 


3. Pyrite. 


4. Pyrrhotite .. 


5. Arsenopyrite_ 


6. Chalcocite. 


7. Chalcopyrite 


8. Bornite. 


9. Tetrahedrite_ 


10. Stibnite 


11. Galenite 


12. Argentite 


Brown, shading 
to green,red, 
and yellow. 


j Green, green- ) 

1 ish-gray. j 

(Greenish or) 
■< brownish > 
( black. ) 


Character. 


Shining. 


Dull 


Gray-black 


Gray-black 


Gray 


Green-black 


Dark-green . 


Dark-gray 


Lead-gray 


Gray 


Gray - black, ) 
pink a n d > 
brown shades, ) 


(Shining, not | 
( magnetic. j 


Shining, is 
magnetic. j 


Shining.., 


Shining 


Shining. 


Shining 


Shining.... 


Shining. 


Very decided shine. 


Very little shine 


During 


Fumes. 


Character. 


Very slight 


Slight. 


Slight. 


Slight. 


j White, very ) 
1 thick. j 


Slight. 


Some fumes..., 


Some fumes.... 


Much .. 


White fumes... 


j Fumes con- ! 
I siderably. f 


Some 


(Each sulphuret will give a little odor of sulphur, but 








































GOLD AND SILVER ORES. 253 


Heating. 


r umes. 


Odor. 


None 


None 


None 


None 


Like garlic. 


None 


None 


None 


some¬ 

times. 


None 

None 

None 


After Heating (when cold). 


Other Char¬ 
acteristics. 

Color of Ore. 

Character. 

(Glows,) 

1 yellow- I 
-! green) 

1 w h e n | 
l hot. J 

( Buff or yel- ) 
i lowish. j 

Dead, dull .... 

Glows. 

Brown. 

Dead, dull .... 

Glows. 

1 Red toblack ) 

•< —m any > 

( shades. ) 

Dead, dull. 



Glows. 

( Red to black 1 
■< — many ) 

( shades. ) 

Dead, dull .... 

(Glows,) 

) swells. j 

( Red toblack 1 
-< — many ) 

( shades. ) 

Dead, dull .... 

Glows,fuses. 

Gray. 

(Shining,) 

-< powder) 

( red. } 

Glows, fuses 

Gray. 

(Shining,) 

-< powder) 


! gray. j 

Glows. 

Gray . 

(Shining,) 

■{ powder) 

( brown. ) 



1 ( Glows, 1 
•< swells, > 
( fuses. ) 

Gray . 

Shining. 

( Swells, ) 
-< melts, > 
( boils. ) 

Gray-green 

( A thin film ) 

•< of shining > 

{ mass. j 

Fuses ...... 

Yellow-green .. 

Shining. 

Fuses. 

Gray. 

( Somewhat ( 

| shining. ) 


Composition. 


Oxide of zinc. 


j Brown oxide 
| of manganese. 

j Red oxide of 
j iron. 


j Red oxide of 
( iron. 


\ Red oxide of 
j iron. 


j Oxide of cop- 
1 per. 


Oxides of iron 
and copper. 

Oxides of iron 
and copper. 


Mixed oxides. 


( Oxide of anti- 
j mony. 

Oxide of lead. 

( Oxideofsilver 
■< s o m e w hat 
reduced. 


it is not to be confounded with the odor of arsenic.) 














































254 


' MANUAL OF ASS A YING. 


An approximate determination of the per¬ 
centage of “ sulphurets ” in an ore can be 
made by mixing io grammes or ioo grains of 
the ore with as much powdered silica and 
twice as much borax glass, placing the mix¬ 
ture in a suitably sized crucible, topping with 
salt, covering, and heating pretty strongly for 
fifteen minutes. Remove, cool, break out 
button as a “matte,” weigh, and multiply 
weight by ten, giving percentage. 

The blow-pipe tests for antimony and zinc 
are not satisfactory, especially in the hands of 
a beginner; hence, I have given the following 
analytical scheme, which, although it seems 
complicated, is really simple. It can be ap¬ 
plied to the most complex ores; for the more 
simple ones some of the steps can be omitted, 
as the student will learn by experimenting with 
it on the various ores and minerals. To prac¬ 
tice it, make a mixture of iron and copper py¬ 
rites, blende, galena, arsenopyrite, sulphuret of 
antimony, and black oxide of manganese. The 
test can be made in an hour’s time. 




GOLD AND SILVER ORES. 


2 55 


Make a mixture, in equal parts, of hydro¬ 
chloric, nitric and sulphuric acids. Place this 
in a beaker, and into it drop some of the 
powdered ore, and heat; then add water , and 
filter. Do not wash. 


Residue and Precipitates. 

Sand, silica, clay; mercury, silver, 
and lead as chlorides; lead, calcium, 
barium, and strontium as sulphates; 
antimony as oxychloride. Wash thor¬ 
oughly with water while on the filter. 


Filtrate. 

Res. and Pre. 

Not needed, 

Remove from filter, 

reject. 

boil with solution of 


tartaric acid, and filter. 


Res. 

Filtrate. 

As first 

Run sulphuretted hy- 

given; re- 

drogen gas through it, 

ject. 

or add water saturated 


with this gas; an orange-colored pre¬ 
cipitate indicates antimony. 


Filtrate. 

Add sulphuretted hydrogen gas, 
and filter from precipitate formed. 


Precipitate. 

Filtrate. 

Mixture of 

Boil off excess of sul- 

various 
sulphu- 
rets; re¬ 
ject. 

phuretted hydrogen, 

add caustic soda in ex¬ 
cess. boil and filter. 

Precipitate. 

Filtrate. 

Iron, chro- 

Add acetic acid in 

mium, al- 

excess, and treat with 

uminium, 
and man¬ 
ganese as 

sulphuretted hydrogen; 
a white precipitate in- 

hydrated 

dicates the presence of 

sesqui o x- 
ides. 

zinc. 


It is difficult to give tests for the highly 
oxidized ores listed. Dull, dead ores in gen¬ 
eral are likely to be in an oxidized condition, 
though not necessarily in the highest state of 
oxidation. If the ore is red and does not 


















2 5 6 


MANUAL OF ASSAYING. 


answer to any test for copper, it will proba¬ 
bly be the red oxide of iron (possibly of lead). 
If it is black, apply the simple tests for cop¬ 
per and manganese given in the appendix. 

But even without a knowledge of the ore, 
gained by observation and experience, or by 
applying tests, its reducing or oxidizing power 
can be determined by certain preliminary and 
arbitrary assays. 

If it is suspected that the ore is reducing, 
prepare the following 

PRELIMINARY CHARGE TO DETERMINE REDUCING POWER. 

A. T. Weights * Gramme Weights .* Grain Weights. * 

Litharge ... iJ A T. 45 grammes 720 grains. 

Ore.* “ ij “ 24 “ 

Salt cover. 

(The above weights of ores are each of 
the respective standard weights taken for the 
crucible process.) 

Weigh first the litharge and brush it on to 

* These weights do not correspond exactly with one another 
(although sufficiently so), nor is it demanded that they should. They 
simply represent the most appropriate quantities for the purpose in 
the several systems of weights. The student can take his choice. 




GOLD AND SILVER ORES. 


2 57 


a clean sheet of black glazed paper, then 
weigh very carefully the finely pulverized ore, 
sampling it as usual; brush it on top of the 
litharge, and mix them thoroughly (indicated 
by the uniform color and character of the re¬ 
sulting compound) with a large steel spatula. 
Pour the charge into a small sand crucible, 
which it should not more than two-thirds fill 
(size “ W ” of the Battersea make, 3 inches 
deep by 2\ inches across, will do nicely) ; tap 
gently till contents are level, sprinkle some 
dry salt over the glazed paper, stir it around 
thereon by half turning over the sides of the 
paper, finally pour it on top of the charge — 
in this manner any of the charge left adher¬ 
ing to the paper is “ dry washed ” into the cru¬ 
cible. There should be about ^ inch salt on 
top. There will then remain an inch or so 
space between top of crucible and the salt, to 
allow for the expansion of the charge when 
fusing. 

Have the fire quite hot, place in it the cru 
cible, covered, bank around it with the hot 






MANUAL OF ASSA YING. 


258 

coals, and heat quickly till contents are in 
quiet fusion, which requires fifteen to twenty 
minutes. 

When satisfied that the charge is well fused, 
remove cover, lift out the glowing crucible by 
means of the long-handled crucible tongs 
(figs. 44 to 48), and tap it gently on a brick 
three or four times (in order to gather into 
one button any little pellets of molten lead 
that may be scattered throughout the fused 
mass), then cover, and let stand till cold. 

When stone-cold, break the crucible, detach 
from all adhering slag the lead button (if 
there is any), hammer into shape as usual, 
and weigh it. 

We shall have one of two alternatives : 

1 st. A lead button. 

2d. No lead button. 

1st Case. A lead button is obtained. 

This result shows that the ore has a reduc¬ 
ing action — the weight of the button will 
indicate its power. 

There will be then one of three results : 



GOLD AND SILVER ORES. 


259 


A. The lead button has a weight less than 
one-half that of the ore. 

B. The lead button has a weight about 
equal to one-half that of the ore. 

C. The lead button has a weight greater 
than one-half that of the ore. 

I take each supposition in turn. 

A. The lead button has a weight less than 
one-half that of the ore. 

Rule. — Multiply the weight of the lead 
button by 20 (to ascertain what the standard 
weights of 1 A.T., 30 grammes or 480 grains 
would produce), and subtract the product from 
the standard weight of button desired (15 
grammes or 240 grains). The result is the 
weight of lead which must be reduced by some 
reducing agent. Divide this by the reducing 
power of the reducing agent to be used, and 
the quotient will be the weight of the reduc¬ 
ing agent necessary to be added in the regular 
assay. 

Examples. — Suppose the A. 1 . or 1^ 
grammes of ore produced a lead button weigh- 



MANUAL OF ASSAYING. 


260 

ing \ gramme, then 1 A. T. or 30 grammes 
would produce Jx20 = 5 grammes, 15 — 5=10, 
so that the lead button lacked 10 grammes of 
the standard weight. We have therefore that 
amount to be reduced by an added reducing 
agent. Taking charcoal as 25 and dividing 
that into the 10 gives us f gramme as the 
weight of charcoal to be employed. 

In a similar manner would we proceed when 
grain weights are used. If 24 grains of ore 
reduced 4 grains of lead, then 4x20 = 80; 240— 
80=160; 160= 25 = 6 f = grains of charcoal to 
be used. 

Should the particular sample of charcoal 
employed possess a greater or lesser reducing 
power than 25, or should argol (reducing 
power about 7^), or flour (reducing power 
about 15), or any other reducing agent be 
made use of, then simply substitute in the 
above calculations the appropriate figures. 

B. The lead butto 7 i has a weight about equal 
to one-lialf that of the ore. 

This case is very simple. The quantity of 



GOLD AND SILVER ORES. 


261 


ore taken for the regular assay will, of course, 
as in the preliminary assay, reduce half its 
own weight of lead (giving buttons of about 
the right size), hence there is needed no ad¬ 
ditional reducing action. 

C. The lead button has a weight greater 
than one-half that of the ore. 

Here we have an instance of too great a 
reducing action, hence the excess of lead must 
be oxidized away, or, to put it more correctly, 
we must supply enough oxygen to satisfy that 
proportion of the reducing elements of the 
ore which would reduce the excess of lead, 
and then they will leave the oxygen of the 
litharge alone. The oxygen-supplying medium 
is nitre. 

Rule. — Multiply the weight of the lead 
button by 20, and subtract from the product 
the standard weight of button desired. The 
result is the excess of lead which is to be re¬ 
tained in the form of litharge by use of nitre. 
Divide this by the oxidizing power of the 





262 


MANUAL OF ASSAYING. 


nitre* used, and the quotient will be the 
weight of the latter to be employed. 

Examples. — Suppose the A. T. or the 
grammes of ore produced a lead button 
weighing 3.15 grammes, then 1 A. T. or 30 
grammes would produce 3.15 x 20=63 grammes, 
63—15 =48—weight of lead to be kept oxidized 
,184-4= 1 2— grammes of nitre to use. 

If the grain weights are used, and the 24 
grains of ore have reduced say 50 grains of 
lead, then 50 x 20 = 1,000 ; 1,000— 240 = 760, 
7604-4= 190= grains of nitre to keep oxidized 
the 760 grains of unnecessary lead. 

The various sulphurets possess varying re¬ 
ducing powers ; hence, by starting with a 
knowledge of the reducing power of each 
kind of sulphuret, and estimating, by the eye, 
the proportion or percentage of whatever kind 
may be in the ore in question, we may ap¬ 
proximate pretty closely to the amount of 
nitre to add in order to oxidize all the sulphur 
but that which we want present to bring down 

*One part of nitre oxidizes four parts (very nearly) of lead. 




GOLD AND SILVER ORES. 


263 


the proper weight of lead, and so can avoid 
making a preliminary assay. The adjoining 
table will be found useful for reference : 


Kind 

of 

SULPHURET. 

Parts of lith¬ 
arge re¬ 
quired to 
c om pletely 
oxidize 1 
part of the 
sulphuret. 

Parts of me¬ 
tallic lead 
reduced by 
1 part of the 
sulphuret. 

Percentage of 
the sulphu¬ 
ret which 
with charg¬ 
es of x A.T., 
30 grms. or 
480 grains, 
will reduce 
a lqad but¬ 
ton of about 
1 5 gram¬ 
mes or 240 
grains. 

Parts of 
nitre re¬ 
quired to 
complete¬ 
ly oxidize 
1 part of 
the sul¬ 
phuret. 

I. Zinc blende . . . 

25 

6 5 

7-7 


2. Manganblende . 

30 

6.7 

7-5 


3. Iron pyrites . . 

50 

8.6 

5 8 

2-5 

4. Arsenopyrite . . . 

40 

7 - 3 * 

6.5 


5. Copper pyrites . 

30 

7.2 

7 


6. Copper glance . 

25 

CO 

CO 

13 


7. Gray copper .. . 

35 

6 

8 


8. Gray antimony. 

25 

5-7 

9 


9. Galena. 

1 8 

2.8* 

18 

a 

~s 


* All the lead of the galena and litharge. 


Should the assayer decide to roast the ore, 

of course it will not be necessary to make a 

♦ • 

preliminary assay to determine its reducing 
power, as the roasting will eliminate the re¬ 
ducing elements. But it should be remem- 



















264 


MANUAL OF ASS A YING. 


bered that the roasting converts the sulphu- 
rets of copper, iron, manganese, and lead, and 
their lower oxides, into the higher oxides of 
the same metals. It will, therefore, make 
their ores highly oxidizing, requiring a greater 
amount of reducing agent in the actual assays, 
and, perhaps, necessitate preliminary assays 
to determine their oxidizing powers, as shown 
in the succeeding paragraphs. 

2d Case. No lead button is obtained. 

This result shows conclusively that the ore 
has no reducing action. It may also have no 
oxidizing action ; but, on the other hand, it 
may. In case it has no oxidizing action, then, 
for the regular assay, take such an amount of 
whatever reducing agent is used as will pro¬ 
duce the proper weight lead button. 


rhus : 




times or 

Grains 

Of ordinary 

Will reduce 

2 \ 

38 

Cream of tartar 

a lead button 

if 

28 

Argol 

*■ of about 15 

I 

16 

Flour 

grammes or 

i 

8 

Charcoal 

240 grains. 






GOLD AND SILVER ORES. 


265 

To determine the exact oxidizing power of 
the ore, prepare and run the following 

PRELIMINARY CHARGE TO DETERMINE OXIDIZING POWER. 

A. T. Weights. Gramme Weights. Grain Weights. 

Litharge.. 1 A.T. 30 grammes. 480 grains. 

Ore. * “ ii “ 24 “ 

Charcoal.. .050 grms. .050 “ J “ 

Salt cover. 

Use a “ W ” crucible, treat in the usual 
manner, and weigh resulting button. 

As in the tests for reducing powers, there 
will be either : 

1 st. A lead button. 

2d. No lead button. 

1st Case. A lead button is obtained. 

The weight of the lead button will, of 
course, vary, giving rise to one of three re¬ 
sults : 

A. The lead button has a weight less than 
one-half that of the ore. 

B. The lead button has a weight about 
equal to one-half that of the ore. 




266 


MANUAL OF ASSAYING. 


C. The lead button has a weight greater 
than one-half that of the ore. 

To proceed in regular order. 

A. The lead button has a weight less than 
one-half that of the ore. 

Rule .— Multiply the weight of the lead but¬ 
ton by 20 (to bring the calculations up to the 
standard weights of i A. T., 30 grammes or 
480 grains), and subtract the product from 15 
or 240. The difference is a part of the amount 
of lead kept oxidized by the standard weight 
of ore employed, and this action is to be neu¬ 
tralized by an extra amount of charcoal. Di¬ 
vide this difference by the reducing power of 
the charcoal used, and the quotient will be the 
weight of charcoal needed. 

Examples. — The figures given were derived 
from assays on an ore which was composed of 
about one-half silica and one-half red oxide 
of iron. The charcoal used had a reducing 
power of 23.4 — that is, one part of the char¬ 
coal reduced 23.4 parts metallic lead from the 
litharge. 




GOLD AND SILVER ORES. 


267 


The charge given was run twice, and but¬ 
tons weighing 0.30 grammes obtained. 0.30X 
20=6.00; 15.00—6.00=9.00= grammes of lead 
kept as oxide by the action of the ore. 9^- 
23.4=0.384= grammes of charcoal to neutral¬ 
ize this action. Hence, 

Grms. Charcoal. Grrns. Lead. 

.050X20 = i.000 to reduce 6.00 

9^23.4 = 0.384 “ “ 9.00 

Or a total of .. 1.384 “ “ 15.°° 

Had there been no oxidizing ore present, 
the 1 gramme charcoal would have reduced a 
button of 23.4 grammes, as stated. It actu¬ 
ally reduced but 6 grammes; hence, 23.4—6= 
= 18.4= grammes of lead kept oxidized by the 
ore, but, as seen, we cared to reclaim only 
9 grammes of this 18.4 grammes — the re¬ 
mainder can be left oxidized. 

About the same calculations in the grain 
system would be as follows : 4.62 grains = 
weight of lead button reduced by f grain 
charcoal; 4.62x20 = 92.4; 240—92.4=147.6 = 
deficiency in grains of lead of a 240 grain but- 





268 


MANUAL OF ASS A VING. 


ton; 147.6 =23.4 = 6.3 = grains of charcoal to 
reduce that deficiency. Hence, 

Grains Charcoal. Grains Lead 

for 0.75X20 = 10.5 to reduce 92.4 

147.6 -4-23.4= 6.3 “ “ 147-6 

Or a total of . 16.8 “ “ 240.0 

B. The lead button has a weight about equal 
to one-half that of the ore. 

In this case simply multiply the charcoal 
and ore twenty times for the regular charge. 
For example, an ore with .050 grammes char¬ 
coal as usual gave me a lead button of 0.765 
grammes ; hence for the regular assay I took 
1 gramme charcoal to 1 A. T. or 30 grammes 
ore to obtain a 15 gramme (15.30) button. 

In other words, the ore oxidizes such a pro¬ 
portion of the charcoal that the remainder of 
the latter is just sufficient to bring down a 
button of the right size. 

C. The lead button has a weight greater 
than one-half that of the ore. 

Here we have an example of too slight an 
oxidizing action, which allows of too great a 






GOLD AND SILVER ORES. 


269 


reducing action on the part of the charcoal, 
resulting in too large a button. There is 
then needed more oxidizing action, which is 
effected by adding an oxidizing agent, or, 
which amounts to the same thing, by lessen¬ 
ing the quantity of charcoal. 

Rule .— Multiply the weight of the lead but¬ 
ton by 20, and divide the product by 15 or 240. 
The quotient multiplied by the original amount 
gives the right quantity of charcoal to reduce 
a 15 gramme or 240 grain button. 

Examples .— Imagine that the charge on 
a certain ore gave a button of 1.10 grammes. 
This multiplied by 20 is 22 grammes, which 
is too large a button ; hence, better diminish 
the quantity of charcoal. If 1 gramme char¬ 
coal with this particular ore brings down a 22 
gramme button (instead of 23.4, the ore ox¬ 
idizing the difference of 1.4 grammes), then 
15 = 22=0.68; 0.68x1 = 0.68 grammes, the 
amount which will reduce a 15 gramme button. 

In grains, let the lead button weigh 17; 17 




2JO 


MANUAL OF ASSAYING. 


grains x 20 = 340 grains ^too large a button) ; 
240^340=0.7; 0.75x0.7=0.525, or say \ grain. 

2d Case. No lead button is obtained. 

This would show that the ore is extremely 
oxidizing, and to learn its precise strength 
necessitates the repeating of the preliminary 
with double, treble, etc., the quantity of char¬ 
coal, or till a button finally is obtained. But, 
in general, it will be safe to use twice the 
weight of charcoal given, or for the regular 
assay 2 grammes or 31 grains where the pre¬ 
liminary produces no lead or a very minute 
button. 

We have previously spoken of certain re¬ 
ducing elements in ores—viz.: sulphur, arsenic, 
antimony, and zinc. Aside from the reducing 
action which they exert upon the litharge, 
tending to produce too much lead, their pres¬ 
ence in an ore is apt to affect the accuracy of 
the crucible assay. Thus the sulphurets may 
combine with oxygen, forming oxysulphurets, 
which possess the undesirable property of 
taking silver with them into the slag, or, if 




GOLD AND SILVER ORES. 


271 


they remain undecomposed, they may easily 
retain some gold. Arseniates and antimoni- 
ates, whether existing naturally in the ore, or 
whether formed by oxidation during the fusion, 
are also liable to keep silver away from the 
lead button. Blende or other zinc ores car¬ 
rying silver may volatilize this metal or retain 
it in the slag. 

The objectionable elements mentioned may 
be gotten rid of in two ways : by oxidation in 
the crucible during the fusion, or by a prelimi¬ 
nary and separate operation known as roasting. 
If the sulphur, etc., are in small quantities, the 
fluxes, litharge and soda, will oxidize them 
into the slag. If in large quantities, nitre 
must be used. It is yet a disputed ques¬ 
tion among assayers whether to roast an ore 
for crucible assay or not. Much can be said 
with truth on each side. If roasting is not 
performed we save the trouble of an extra 
operation, and the danger of loss which extra 
steps are always likely to cause, including the 
possibility of volatilizing silver by too great a 



272 


MANUAL OF ASSAYING. 


heat in roasting. On the other hand, if roast¬ 
ing is not performed, and nitre is not used, 
there are the various chances of loss of pre¬ 
cious metal already described. If nitre is 
used, there is danger of mechanical loss by 
the foaming of the charge, which may overflow 
the crucible or leave lead sticking to the sides, 
high up; or if too much nitre be taken, the lith¬ 
arge may not be reduced, so care must be ex¬ 
ercised when using it. My own experience 
with beginners is that they are more success¬ 
ful when they previously roast refractory ores, 
than when they omit this step. It certainly 
brings the ore into a much more workable 
condition, as the oxides of iron and copper 
which are usually left are easily treated. With 
any particular ore the safest way to proceed 
is to run duplicate or triplicate assays on both 
the roasted and unroasted sample, and then to 
adopt or dispense with the roasting accord¬ 
ingly as the results are richer with or without 
it. For the benefit, then, of learners, for 
whom this book is written, and not for ad- 



2 73 


GOLD AND SILVER ORES. 

vanced assayers, I give herewith a very care¬ 
ful description of the manner of performing 
th is important operation. 

Roasting .—Weigh the ore carefully, sam¬ 
pling as usual. Next transfer it to a sheet of 
black glazed paper, and mix with it about its 
own bulk of fine charcoal. The latter is usu¬ 
ally recommended only when arseniates and 
antimoniates are present or likely to be formed 
by a plain roasting ; but I consider it advisable 
to use it every time, for one cannot always 
tell when small quantities of arsenic and an¬ 
timony are in the ore, besides which, the char¬ 
coal aids in expelling the sulphur, and in indi¬ 
cating the termination of the roasting. At 
the worst, it can do no possible harm. If the 
ore should contain much sulphide of lead 
(galena) or sulphide of antimony (antimony 
glance), both of which are quite easily fusible, 
add to the ore and charcoal on the paper 

some fine sand or precipitated silica, and mix 

• 

all well together, for without this addition the 
minerals while roasting would soon fuse, cake 




274 MANUAJL % OF ASSAYING . 

together, and adhere to the dish or pan, thus 
ruining the assay. The proportion of silica 
to use depends upon the percentages of the 
minerals named, it increasing as they increase 
— roughly speaking, it can be employed bulk 
for bulk. 

In case the ore is a sulphide or mixture of 
sulphides (of whatever metal or metals), with 
very little or no gangue, it is best to add silica, 
to the amount of at least three-fourths of the 
weight of ore. 

The contents of the glazed paper are now 
brushed into either a frying-pan (page 131), 
or a clay roasting dish (page 112), accord' 
ingly as an open fire or the muffle is to be 
used. The frying-pan should be protected 
by a coating of dry chalk or ruddle (or a 
water paint of either can be used and the pan 
dried), or plumbago. The roasting dish may 
be similarly protected, but it is not so neces¬ 
sary. If the standard weights of 1 A. T., 30 
grammes, or 480 grains is used, the ore mix¬ 
ture can be roasted in the largest roasting 





GOLD AND SILVER ORES. 


2 75 


dish which will go in the muffle ; but above 
those weights use the frying-pan, or else roast 
several charges in the dishes, and unite them 
for fusion. 

Place the roasting dish, with contents, in 
the forward part of the muffle, before the latter 
has reached a dull red heat. The ore is to 
be continually stirred with a stout wire, hav¬ 
ing a loop at the end at right angles to the 
wire, ' a. In a little while, minute 

sparks will be thrown off, and the ore will 
begin to glow in places like burning charcoal. 
Stirring should be continued till the glowing 
ceases (by which time there will be little 
danger of fusion), and the whole seems of 
one color, and yielding to the stirrer like dry 
sand. The dish can now be moved back to 
the hottest part of the muffle, and left un¬ 
stirred for some little time. When, on bring¬ 
ing out to the open air and stirring, the ore 
gives off neither fumes nor odor, the opera¬ 
tion is finished, the ore being now “sweet.” 
Let cool, and examine. 






2j6 


MANUAL OF ASSAYING. 


The roasted ore should be of a dull, dead, 
earthy color (usually some shade of red or 
black), having no metallic lustre, containing 
no large, hard lumps, and having no portions 
adhering to the dish. See that all the char¬ 
coal is burnt out. Should the ore contain 
many lumps, grind in a mortar, mix with 
charcoal, return to the dish, and repeat the 
roasting. 

If the assayer is too busy to spare the time 
needed for stirring, let him take the dish, and 
spread its contents out thinly, or ridge the 
ore from the center to the edges, so as to 
increase the surface exposed, and place it in 
the muffle, and warm it gently for a time ; 
then increase the heat for about the same 
length of time; finally heat quite hot. Take 
out dish, cool, grind finely, return to dish, and 
roast again. Repeat the roasting two, three, 
or more times if necessary. All this will 
occupy time, but not the direct attention of 
the assayer. 

The roasting in the pan is done similarly. 



GOLD AND SILVER ORES. 


2 77 


Whether open-air pan roasting, or dish in 
muffle roasting is performed, guard against 

too high a heat at first, as that may cause 

# 

fusion, or too sudden a delivery of the vola¬ 
tile metals mentioned, which may carry off 
silver, or even too great heat at any stage of 
the roasting, tending to volatilize silver or 
£old from some of their combinations. 

The roasting with charcoal is supposed to 
decompose all sulphates, arseniates, and anti- 
moniates, and to expel them ; but where the 
ore was or contained copper pyrites, a certain 
quantity of sulphate may remain unchanged. 
Hence, with ores of this nature, mix the 
roasted ore with from one-fourth to one-half 
its weight of fine and dry carbonate of ammo¬ 
nia. Return to dish, cover with an inverted 
roasting dish, and place in a moderately warm 
part of the muffle till no odor of ammonia 
can be perceived. The sulphate of copper is 
converted into sulphate of ammonia, which, 
being very volatile, is quickly driven off. 

If the laboratory is provided with gas, the 



278 


MANUAL OF ASSAYING. 


ore can be roasted in the usual roasting dish 
over the Fletcher burners or the Fletcher 
roasting furnace, illustrated on page 74, which 
will work very nicely, as the temperature can 
be regulated to any degree. 

Methods of the crucible assay. —There are 
two general methods or systems of crucible 
assays in use in this country. The first, more 
ancient, better known, and more commonly 
used one employs an excess of litharge, and 
we can therefore consistently call it the lith¬ 
arge crucible process. Mr. C. H. Aaron, in 
his very valuable little work on assaying, 
designates it as the first system, while another 
method, which he is the first to describe, he 
calls the second system. In justice to him, I 
prefer to call it Aarons crucible process. 

The distinction between the two systems is 
this: The first mentioned uses litharge for 
two purposes, to furnish lead enough for a 
lead button to retain the gold and silver, and 
to aid in fluxing the ore, hence an excess of 
the litharge is employed. The second uses 




GOLD AND SILVER ORES. 


279 


just enough litharge to provide lead for the 
lead button. 

In the first, the excess of lead not only 
slags off the gangue, but it oxidises all the 
base metals, save lead, and takes them also 
into the slag. In the second, the gangue is 
slagged by soda, borax, or silica, while the 
base metals are either volatilized, united with 
sulphur into a matte, or combined with iron. 

Any ore may be assayed by either of these 
processes, but each is better suited to certain 
classes. 

Mr. Aaron argues that while an assay by 
the litharge process “ is quickly made, and 
generally gives accurate results,” yet “ it has 
the disadvantage of requiring considerable 
modification for the various ores, as to the 
duxes proper, and to the reducers or oxidizers 
by which the production of lead is controlled. 
Sometimes a preliminary assay is necessary.” 

For his process he claims the following 
advantages : “ The right quantity of lead 

may nearly always be got at once, for, ah 




2 So MANUAL ON ASSAYING . 

though any lead which the ore may contain 
will inevitably come down together with that 
from the litharge used, yet this can be allowed 
for by reducing the quantity of litharge, or 
omitting it. As litharge yields ninety-three 
per cent of lead, it is not difficult to make 
the adjustment nearly enough. Galena con¬ 
tains eighty-six per cent of lead ; hence, if the 
ore is nearly pure galena, but little litharge is 
needed. The method requires but slight 
modification for different ores, and may with 
little disadvantage be made universal. The 
button is never much contaminated by cop¬ 
per, as it often is in the other system, unless 
a very large proportion of litharge is used, 
which is disadvantageous in some ways. The 
crucible is but little attacked, and the assay is 
not liable to boil over. The method is es¬ 
pecially useful for ores carrying much galena 
or other sulphuret, and when copper in any 
form is present.” An additional advantage, 
resulting from the above, as remarked by Mr. 




GOLD AND SILVER ORES. 


28l 


Aaron elsewhere, is the saving in litharge 
and crucibles. 

My own experience with Mr. Aaron’s pro¬ 
cess shows that it takes considerably more 
time than does the litharge process, and that 
beginners find it more difficult to operate, 
and to get satisfactory results. 

The student can take his choice of either 
process, apply it to any ore, and experiment 
till he strikes that combination of correct 
proportion of the ingredients of the charge, 
degree of heat, and length of time in furnace, 
which will give him the best results. 

Let him remember that the principles of 
fluxing are true for either process. 

Preparation of the charge. After having 
obtained a knowledge of the ore by tests 
based upon the study of all the preceding, 
the proper charge is made up. Further on I 
have given special charges and directions for 
certain ores, but here I make it only general. 

The most convenient and commonly used 
amount of ore is either one of the standard 




282 


MANUAL OF ASSAYING. 


weights I have so frequently spoken of, viz.: 
1 A. T., 30 grammes, or 480 grains. If a 
very low grade gold ore is under examination, 
the above quantities can be doubled, trebled, 
or quadrupled, or, if necessary, ten or even 
twenty times the standard weight may be 
used. But such large quantities, with the 
fluxes accompanying, are rather difficult to 
handle, so that it is best to run several 
charges of the standard weight (or, perhaps, 
double it), and to unite the resultant buttons 
by scorification. If it should happen that 
there is not enough of the ore to. make a fair 
charge (say not half the standard weight), 
then do not trouble about the crucible process 
at all, but treat the sample by scorification. 

Bi-carbonate of soda, or, as it is commonly 
called, soda, is used in every crucible assay. 
Although not absolutely necessary, still a 
mixture of it with carbonate of potash gives 
somewhat more fluid slags. About one part 
of the latter to four parts of the former is a 
good proportion. Considering the ore as one 




GOLD AND SILVER ORES. 


28 3 


part, the amount of soda (or of soda and car¬ 
bonate of potash together) varies from one- 
half to three parts. A safe quantity to use is 
two parts. 

Litharge is also used in all crucible assays 
save those of ores very rich in lead. The 
proportion varies from one part to eight 
parts—one to two parts being the usual 
range. 

Silica is usually employed only for ores full 
of lime, magnesia, baryta, etc.; in short, for 
those whose gangues are basic, or when the 
ore contains no gangue; but I make it a uni¬ 
versal rule to use it in all crucible assays. 
For those ores which have no gangues or are 
basic, it is certainly needed. For those which 
contain silica I still add it, to be certain to 
convert the excess of lead over and above 
that required for the standard weight of lead 
button into silicate of lead, a most efficient 
flux. This for ores worked by the litharge 
process. In those treated by Aaron’s pro¬ 
cess, the added silica converts the soda into 





284 


MANUAL OF ASS A YING. 


silicate of soda (or soluble glass), a good 
flux, although not so powerful as the lead 
glass. For pure carbonate of lime and similar 
gangues, use the same weight of silica as of 
ore. For pure quartzose ores, one-half the 
weight of ore. For less pure quartz, three- 
fourths the weight of ore. In brief, my final 
advice is, not to be afraid of using plenty of 
silica in crucible charges. 

Borax is best used in the form of borax 
glass. For quartzose ores, none is absolutely 
needed, but about 10 per cent the weight of 
ore does no harm, and seems to help the 
fusion. Strongly basic ores need 50 per cent 
of borax glass. As they diminish in lime, 
etc., down to quartz ores, diminish the borax 
glass down to 10 per cent. 

Charcoal and other reducing agents, and 
the oxidizing agent, nitre, are to be used 
according to their several powers and as the 
ores vary. 

It should also be remembered that where 
gas furnaces are constantly used, there will 



GOLD AND SILVER ORES. 


285 

not be required so much reducing agent in 
the crucible charges as in those made up for 
solid fuel furnaces, the flame and heat of the 
gas furnaces being more reducing. 

A cover of salt is to be invariably used. 

Select the crucibles, which should be free 
from cracks and flaws. A good size for the 
charges to go with the standard weights of 
ore is inches wide by 4^ inches deep, 
outside measurement (size “S” of Battersea 
make). Clean the crucibles inside if they 
need it, and number or letter each by means 
of liquid ruddle, in several places and in large 
characters, that there may be no difficulty in 
identifying them after fusion. 

Weigh out next the soda for the charge, 
and brush on to a clean piece of black glazed 
paper. Next weigh the litharge very care¬ 
fully, and brush on top of the soda. I he 
silica, weighed approximately, is followed by 
the ore, charcoal, or other reducing agent, or 
nitre, each weighed carefully. If sulphur is 
used, it can come next. Finally, weigh the 



286 


MANUAL OF ASSA YING. 


carbonate of potash, rapidly and but approx¬ 
imately, as it quickly absorbs moisture from 
the atmosphere; transfer to the paper, and 
mix everything thoroughly. 

Brush the charge into the proper crucible, 
which it will probably fill two-thirds, tap gen¬ 
tly till the contents are level, drop the weighed 
borax glass on top, and cover with about one- 
half inch common salt. If nails are used, in¬ 
sert them in the charge before the salt is 
added. 

Another method of charging or “dressing” 
the crucibles is to pour the soda into the cru¬ 
cible, then the ore, following with the other 
fluxes, and mixing all together in the crucible 
with any convenient utensil, as a spatula, 
spoon, or glass rod. 

The marking of the crucibles may be dis¬ 
pensed with if the fusions are made in regular 
order; but in this case, great care must be 
exercised, for doubt once entertained as to 
the identity of any crucible may dispel faith 
in those following or preceding it, 



GOLD AND SILVER ORES. 


287 


Running' the Crucibles in the Fire. 

Have the fire quite hot, and place on the 
coals the crucible, holding it with the tongs 
with one hand, and banking it around with 
the fuel till it sets firmly and uprightly in 
place. Place the cover on, and surround with 
coke, charcoal, or coal, as the case may be. 
Coke works the best when of about the size 
of an egg, charcoal may be in somewhat 
smaller pieces. The finer particles of either 
are often useful when the fire gets too hot, 
by choking the draft. Arrange the draft 
and damper so as to permit of a gradually 
increasing heat. 

Occasionally examine the crucible to see if 
all is working smoothly. In from twenty-five 
to forty-five minutes the contents of the cru¬ 
cible should be in quiet fusion. The length 
of time that a charge requires to be thor¬ 
oughly melted in depends so much upon the 
ever varying conditions of temperature of the 
furnace, character of ore, size and nature of 




288 


MANUAL OF ASSAYING. 


charge, etc., that no exact rule can be given — 
only see that the charge is fused. 

When satisfied of this, remove cover, lift 
out the glowing crucible by means of the long- 
handled crucible tongs, tap gently, cover, and 
let cool, or pour into the scorification mould, 
which will hold the button and some of the 
slag ; the excess of the latter can run to 
waste. 

If nails have been used, before tapping or 
pouring rinse each nail in the slag, tap and 
remove. No lead should adhere to them. 

Crucibles that have had their contents 
poured out can be employed a second time, or 
even more often. In case of ores that have 
shown little or no gold or silver this may do, 
but with ores of any richness it is a danger¬ 
ous experiment. Accuracy should never be 
sacrificed to a spirit of false economy. 

Never try to cool a crucible by dipping it 
into, or holding it under, cold water, as the but 
partially cooled lead is liable to separate into 



GOLD AND SILVER ORES. 


289 


globules of various sizes, incurring danger of 
loss. 

When stone-cold, break the crucible by 
striking it a few sharp blows down one side 
with a hammer. If skilfully done, the cruci¬ 
ble will separate in halves the entire length, 
exposing the lead button. Such a section 
would appear about as here 
shown, showing at the bottom 
the lead button containing the 
gold and silver, above it the 
slag, and topping all a layer 
of fused salt. (The thin body 
just above the button shows Fig. 129. 

how a “matte” would appear were any formed 
by the fusion of a sulphuret.) 

From the broken crucible or the poured 
charge in the mould save a piece of the slag 
for future examination and comparison. It 
should be uniform in color and composition 
— the former will vary with the character of 
the ore and proportions of the ingredients of 
the charge. If the latter has been poured, 









290 


MANUAL OF ASSAYING. 


the crucible should be but little corroded, and 
smoothly lined with a thin glaze of the slag, 
and retain no lumps of semi-fused nature or 
pellicles of lead. 

Free the button from the slag, which it 
should easily and cleanly leave, hammer into 
shape, as usual, and mark. It may be well to 
weigh it, so that the assayer may know 
whether he has used the proper quantity of 
reducing or oxidizing agent, etc., or to modify 
the treatment on the same or similar ores in 
the future. 

If the button is too large, it may be re¬ 
duced by scorification ; but this introduces an 
additional step, and may not give quite so 
accurate a result. 

Finally, cupel the button, weigh, part, in¬ 
quart, etc., as previously directed. 

With all ores poor in silver, deduct the 
silver known to be in the litharge, according 
to the amount of the latter employed. 

General Charges .—From what has been pre¬ 
viously written of the varying characters of 



GOLD AND SILVER ORES. 


29I 


ores the student can see how difficult, if not 
impossible, it is to give a charge of fluxes, 
etc., which shall satisfy every ore. Still, there 
are a few general formulae useful to have and 
quite easy to remember, which can be more or 
less modified to suit any particular ore. 

Mitchell’s charge for all gold and silver ores. 

Ore. 1 part. 

Soda. 1 “ 

Litharge.5 parts. 

Borax glass.1 part. 

Nitre or charcoal and always a cover of salt. 

The above in each of the three systems of 
weights : 


A. T. Weights. 

Gra m m e Weigh ts. 

Grain Weight . 

Ore.1 

A.T. 

30 grammes 

480 grains= 1 

Soda.1 

<« 

3° “ 

t—• 

II 

0 

00 

Tt- 

Litharge .... 5 

<< 

150 “ 2,400 “ =5 

Borax glass.. 1 
Salt cover. 

<< 

3 ° “ 

480 “ = I 


A similar but more commonly used propor¬ 
tion is : 









292 


MANUAL OF ASS A YING. 


Ore.1 part. 

Soda.1 “ 

Litharge.if 

Borax or silica, nitre or charcoal, and salt cover. 


Or, to put it more conveniently : 


A. T. Weights. 

Gramme Weights. 

Grain Weights. 

Ore. t A.T. 

30 grammes 

480 

grains=i oz. 

Soda.1 “ 

30 “ 

480 

U _ J (( 

Litharge .. if* “ 
Salt cover. 

5° 

800 

« — .2 « 
~~ 1 5 


Mr. George L. Stone has published the fol¬ 
lowing as a universal flux for basic silver ores 
those in which the gangue is lime, ba¬ 
ryta, etc. — for instance, the three spars, calc- 
spar, heavy-spar, and fluor-spar) : 

Bi-carbonate of soda.9 parts. 

Borax glass. 3 “ 

Argol.1 part. 

“ Mix thoroughly, and keep on hand ready 
for use. For one-third assay ton of ore fill 


* if A.T. or i.66| A.T. cannot be exactly weighed with the 
A.T. weights, but the sum of the following weights will approxi¬ 
mate it sufficiently : 1 A.T. +0.50 + 0.10-1-0.05 = 1.65. 















GOLD AND SILVER ORES. 


293 


the crucible about two-thirds full of the flux, 
adding two or three iron nails if the ore con¬ 
tains much sulphur.” 

chapman’s crucible flux. 

“A useful flux, employed largely by the 
writer during the past ten or twelve years, 
and which has been found, both in his own 
practice, and in that of others, to yield good 
results in all general cases, has the composi¬ 
tion given below : 

3 lbs. carb. soda, 

2 “ dried borax, 

J lb. cream of tartar, 

2 oz. white sugar. 

“ The re-agents in these proportions must 
be intimately intermixed. The above quanti¬ 
ties will dress from 18 to 20 crucibles, when 
about 25 grammes of ore are taken for assay.” 
(Chapman’s Assay Notes, 1881, p. 31.) 



294 


MANUAL OF ASSAYING. 


aaron’s general formula. 


(For ores to be worked by his second system. 

See page 278.) 

Ore. 

i part. 

Soda. 

3 parts. 

Litharge. 

1 part. 

Borax. 

i part. 

Sulphur . 

* “ 

Flour. 

1 “ 

To- 

Iron. 

3 nails. 

Glass. 

Salt to cover. 



“ Melt, and leave in strong fire about twenty 
minutes after fusion.” (Aaron’s Assaying, 
1884, p. 53.) 

The above amplified as usual is as follows : 

A. T. Weights. Gramme Weights. Grain Weights. 

Ore.1 A. T. 30 grammes 480 grains= 1 oz. 

Soda.3 “ 90 

Litharge .. 1 “ 30 

Borax .... \ “ 15 

Sulphur_“ 3 

Flour. tV “ 3 

Iron.3 nails. 

Glass. 

Salt cover. 


1,440 

(i 

= 3 

u 

480 

a 

= 1 

a 

240 

a 

= \ 

a 

48 

u 

— tV 

u 

48 

u 

— tV 

it 
















GOLD AND SILVER ORES. 


2 95 


The same excellent authority, Mr. Aaron, 
gives the following charge for “ ordinary ores 
containing little or no sulphuret, some quartz, 
clay, lime, iron, oxide, etc. ” : 


Ore. 

Soda. 

Litharge ... 
Dried borax 

Flour. 

Salt cover. 


i part. 

1 “ 

2 parts, 
i part. 

* “ 


“ Fuse quickly ; keep in furnace five to ten 
minutes after subsidence.” (Aaron, page 49.) 

Putting the above in the three systems of 
weights, and reducing the flour one-half, since 
the quantity given is based on & standard of 
\ A. T. ore, we have the following : 

A. T. Weights. Gramme Weights. Grain Weights. 


Ore.1 

A. T. 

30 

grammes 

480 grains^ 1 

oz 

Soda.1 

u 

30 

u 

480 

“ =1 

<« 

Litharge ... 2 

tt 

60 

(i 

960 

“ =2 

(« 

Dried borax. 1 

a 

3 ° 

a 

480 

“ =1 

<( 

Flour.1 

Salt cover. 

grm. 

1 

grm. 

16 

<< 



The following and concluding charge of 













296 


MANUAL OF ASS A YhVG. 


this section is one I have used many times 
for ores similar to those above sooken of; 

A 

that is, not containing much sulphuret, or 
oxidized metal; ‘‘dry ores,” in short, or, as 
Mr. Aaron calls them, “ordinary ores.” The 
nature of the gangue is unimportant, as I 
have gotten as perfect and as vitreous slags 
from pure limestones as from pure quartzose 
rock, by using it. 

A. T. Weights. Gramme Weights. Grain Weights. 


Ore. 

1 

A. T. 

3 ° 

grammes 

480 grains^i 

Bi-carb. soda 


U 

45 

u 

720 “ =1$ 

Carb. potash 

i 

<< 

15 

<( 

240 “ = \ 

Litharge ... 


a 

45 

<« 

720 “ =i£ 

Silica. 

1 

u 

30 

<< 

W 

II 

0 

00 

Borax glass. 


(< 

i 5 

u 

240 “ = \ 

Charcoal ... 

Salt cover. 

T 6 o 

grms. 

A 

u 

9 i “ 


The charcoal is used on the basis of a 
reducing power of about 25. Time in fire, 
about one-half hour. 

Special charges and directions .—I shall here 
give charges for certain well known ores, as 
examples of the varying modes of treatment 







GOLD AND SILVER ORES. 


297 


These are iron pyrites and its oxide, the sul- 
phurets of copper and their oxides, and 
galena. All other ores and combinations can 
be worked by some one of the general or 
special methods, or some slight modification 
of one of them. 

I.-IRON PYRITES. 

Pyrite, the true iron pyrites, is one of the 
most widely distributed of minerals, is found 
in the rocks of every age, and is a common 
and abundant source of gold. There are 
many varieties of it, and of another and simi¬ 
lar mineral, pyrrhotite, which have received 
many names, as pyrites, iron pyrites, pyrite, 
marcasite, mundic, bi-sulphuret or bi-sulphide 
of iron, sulphuret or sulphide of iron, and 
pyrrhotite, magnetic pyrites, magnetic iron 
pyrites, magnetic sulphuret of iron, magneto¬ 
pyrites, etc. But since the assay treatment 
makes no mineralogical distinctions, I shall 
include under the one simple and well known 
heading of “iron pyrites” any combination 





298 


MANUAL OF ASSAYING. 


of iron and sulphur, with or without a gangue, 
and direct accordingly. 

Iron pyrites has frequently united or asso¬ 
ciated with it varying amounts of other met¬ 
als, as nickel, cobalt, copper, zinc, manganese, 
arsenic, antimony, etc. If in small quanti¬ 
ty, none of these need influence the charge 
or manner of treatment. If in large quantity, 
making either a compound mineral, or a com¬ 
bination of various minerals, they may necessi¬ 
tate some variation in the mode of treatment. 

Since, as stated, iron pyrites is found in 
rocks of every geological epoch, we may ex¬ 
pect to have every kind of gangue ; but, by 
remembering the rules already given, that 
acid and basic gangues are to have basic and 
acid fluxes, no trouble need be feared. Sil¬ 
ver, if present, will come down with the gold. 

METHOD A. 

Desulphurization by a preliminary roasting. 

For the ore without any gangue, or for 





GOLD AND SILVER ORES. 


*99 


“concentrates,” mix 1 part (1 A. T., 30 
grammes, 480 grains) with 1 part of silica. 

Mix the above, or the ore alone, if it has a 
gangue, with its bulk of fine charcoal, and 
roast according to pages 273-278. 

After roasting, add the other constituents, 
so that the total charge will be as follows : 

CHARGE. 


A. T. Weights. 

Gramme Weights. 

Grain Weights. 

Ore (roasted). i A.T. 

30 grammes 

48ograins=i oz. 

Bi-carb. soda . 1J “ 

45 

u 

H©* 

w 

II 

># 

># 

0 

N 

Carb. potash . \ “ 

15 

<{ 

240 “ = i “ 

Litharge.1 £ “ 

45 

it 

720 “ = l£“ 

Silica.1 “ 

30 

t( 

480 “ = 1 “ 

Borax glass .. ^ “ 

6 

K 

96 “ = | “ 

^Charcoal.... f grm. 

f 

U 

iii “ 

Salt cover. 





Use an “S” Battersea crucible (4! inches 
deep, 4^ inches across, outside measurement). 
If it is feared that a little sulphuret may re¬ 
main unoxidized during the roasting, one nail 
may be pushed into the charge, and is to be 
removed immediately after fusion. 

* Assumed to have a reducing power of 25. 






3 °° 


MANUAL OF ASSAYING. 


Time in fire about thirty minutes, or, at all 
events, let remain heating for ten minutes 
after the charge has settled into quiet fusion. 

It is well to bear in mind that iron pyrites 
(pyrite) loses exactly one-third of its weight 
by being roasted into the red oxide, so that 
one part of the sulphuret becomes but two- 
thirds of a part of oxide. (The varieties of 
pyrrhotite lose from one-seventh to one-eighth 
in weight.) Further, that one part of the 
red oxide keeps oxidized about i-|- parts of 
litharge, or, more exactly speaking, it oxidizes 
the charcoal which would reduce i^- parts 
litharge. 

The charge given, as stated, is for an ore 
almost, if not entirely, iron pyrites. From 
such a large percentage it may run down to a 
very small amount of the mineral, the gangue, 
of a necessity, increasing accordingly. If the 
gangue is silicious, diminish the added silica 
in the charge as the proportion of gangue 
increases, but do not altogether omit it for 
even the most silicious ore — retain from J to 




GOLD AND SILVER ORES. 


301 


\ a part. If the ore is limey or otherwise 
basic, retain the full part of silica, and increase 
the borax glass to ^ a part. 

The charcoal (or any other reducing agent) 
must, of course, be decreased as the iron py¬ 
rites decreases, for the less there is of the 
latter the less oxidizing power there is in the 
roasted ore. The actual quantity of charcoal 
to use on any particular ore is determined by 
either guessing the percentage of sulphuret 
in the unroasted ore, or by making a prelimi¬ 
nary assay to determine the oxidizing power 
of the roasted ore. Instead of doing the lat¬ 
ter additional work, the assayer can come 
closely enough to the size of the button he 
wants (15 grammes or 240 grains) by adding 
charcoal as the redness of the roasted sample 
increases, and vice versa, as follows (the char¬ 
coal considered to be of a reducing power 
of 25) : 




302 


MANUAL OF ASS A YING. 


Grammes of 

Color of Roasted Ore. Charcoal to Use. 

Very deep red. 0.850 

Deep red.0.800 

Medium deep red.0.750 

Red .0.700 

Medium light red.0.675 

Light red.0.650 

Very light red.0.625 

Very light rose or pink.0.600 


The slags from crucible runnings of the ore 
we are discussing, if the fusions have been 
properly conducted, will always be homogene¬ 
ous and glassy in texture, and will be translu¬ 
cent or transparent when not much iron oxide 
is present, opaque when the oxide prepon¬ 
derates ; in color, ranging from very light 
green to a black, with a greenish or grayish 
tint accordingly as the iron oxide increases. 

METHOD B. 

Desulphurization during the fusion . 

With ores treated by this method we do 
not get rid of the sulphur of the iron pyrites 
by a preliminary operation, but do the desul- 











GOLD AND SILVER ORES. 


303 


phurizing during the fusion by the oxidation 
of all the sulphur (save a sufficient quantity 
to bring down a 15 gramme or 240 grain but¬ 
ton) by means of nitre. 

CHARGE. 


For pure pyrites ( i.e free from gangue) and “concentrates.” 


A. T. Weights. 

Gramme Weights. 

Grain 

Weights. 

Ore.1 

A.T. 

30 grammes 

480 grai 

ns= 1 oz 

Bi-carb soda . i| 

u 

45 

720 “ 

= 4 “ 

Carb. potash. £ 

it 

i 5 

240 “ 

= i“ 

Litharge .... ij 

a 

45 

720 “ 

— ,! « 
— ‘V 

Silica.1 

u 

30 “ 

480 

= 1 “ 

Borax glass .. ^ 

u 

6 

96 “ 

= t“ 

Nitre.2 

Salt cover. 

it 

54 “ 

00 

0 



Use Battersea “J” crucible (6|- inches deep, 
4f inches across, outside measurement). 

Time, about half an hour. 

The oxidizing power of nitre varying, the 
amount used may have to be altered some¬ 
what according to its strength, as determined 
on page 176. The quantity taken was deduced 
from the following calculation — for example, 
the weight in grammes: 1 gramme iron pyrites 
reduces 8.6 grammes lead (according to the 









304 


MANUAL OF ASSAYING . 


table on page 263); hence, 1.74 grammes py¬ 
rites will reduce about 15 grammes lead; 30— 
1.74 = 28.26 = grammes of iron pyrites to be 
oxidized. 1 gramme iron pyrites requires for 
oxidation from 2 to 2\ grammes nitre; hence, 
28.26x 2 = 56.5= grammes nitre to use. 

Run in good fire, twenty minutes to fusion, 
ten afterward. Slag brown-black, vitreous, 
opaque. If the button is at all brittle from 
presence of sulphur, add lead and scorify. 

For other ores, as the iron pyrites diminishes 
(and the gangue increases), lessen the silica 
and nitre. The quantity of the latter to use 
is determined by experience and experiment, 
or by ascertaining the reducing power of the 
ore, for which latter see page 256. 

method c. 

Desulphurization during the fusion . 

This method of treating the ore is to use 
an excess of nitre, i.e. y more than enough to 

o 

oxidize all the sulphur, bringing everything 
into quiet fusion, and then throwing down 



GOLD AND SILVER ORES. 


305 


the proper weight of lead by adding a known 
amount of some reducing agent, as charcoal, 
or a mixture of charcoal and litharge, or 
galena and litharge. The reduced lead in its 
passage down through the molten charge ab¬ 
sorbs the gold and silver. 


CHARGE. 

For iron pyrites with no gangue, or concentrates. 

A. T. Weights. Gramme Weights. Grain Weights. 


Ore . i A.T. 30 grammes 

48ograins=i oz. 

Bi-carb. soda. “ 45 

720 

“ =ii“ 

Carb. potash. \ “ 15 “ 

240 

“ = i “ 

Litharge .... 6 “ 175 

2,880 

“ =6 “ 

Silica.2 “ 60 

960 

“ =2 “ 

Borax glass.. i “ 30 

480 

U _ J u 

Nitre.2| “ 75 

1,200 

N# 

hn 

II 

Salt cover. 



Use a “ J ” crucible. 



Begin with a very gentle 

heat, 

and grad- 


ually bring up to a full red heat (thirty-five 
minutes). When in full fusion add the fol¬ 
lowing weight of charcoal wrapped in tissue 
paper (considering the weight of the paper 

as charcoal) : 

1 gramme, or 15^ grains. 







3°6 


MANUAL OF ASSA YING. 


When again in quiet fusion (five minutes), 
remove and tap, or pour. Slags brownish- 
black, vitreous, opaque. 

For less pyritic ores use less nitre. 

METHOD D. 

Desulphurization with iron. 

CHARGE. 

Make up the ore with fluxes as follows: 


A. T. Weights. 

Gramme Weights. 

Grain 

Weights. 

Ore.i A.T. 

30 grammes 

48ograins=i oz 

Bi-carb. soda, “ 

45 

720 

“ = 4 “ 

Carb. potash. £ “ 

15 

240 

“ = i “ 

Litharge .... “ 

45 

720 

“ = 4 “ 

Silica.i “ 

30 

480 

u _ j u 

Borax glass.. y “ 
Iron nails, 6. 

Salt cover. 

6 

96 

a 


Use “S" crucible. Time, one-half hour. 

Tie the nails with wire together, and stick 
the bunch into the charge, points down. 
After fusion, should any ‘‘matte” be formed, 
it must be scorified, with the lead button, to 
a pure and malleable condition. 

Slags brown-black, vitreous, opaque. 






GOLD AND SILVER ORES. 


307 


METHOD E. 

Converting the iron pyrites into matte . 
Aaron s process ( modified ). 

CHARGE. 

For concentrated pyrites. 

A. T. Weights. . Gramme Weights. Grain Weights. 
Ore.1 A.T. 30 grammes 480 grains^ ioz. 


Bi-carb. soda.3 

<C 

90 

<< 

1,440 

“ —3 “ 

Litharge .... ^ 

<< 

*5 

<< 

• 

240 

“ = i “ 

Silica.1 

u 

30 

u 

480 

U _ J «< 

Borax glass.. 

u 

15 

a 

240 

“ = i “ 

Nitre.-J 

Iron nails, 6. 

Salt cover. 

u 

12 

a 

l8+ 

<< 


Use “ S” crucible. Time forty minutes. 

The nitre is to oxidize the excess of sul¬ 
phur ; i.e. f that over and above the amount 
necessary to reduce all of the litharge, and 
yet not enough of this re-agent is used to 
prevent the formation of a matte. 

Slag coal-black, vitreous, opaque. 

Mr. A. H. Low, of Argo, Colo., has given 
me a good hint in the crucible running of sul- 
phuret ores, which I herewith note. Make 







3°8 


MANUAL OF ASSAYING. 


the fusion in the usual manner, and when it is 
supposed to be completed, take out, and pour 
off as much of the slag as possible without 
losing any of the lead. The button can now 
be easily seen, and if all the sulphur has not 
been driven off, replace the crucible in the 
fire at an angle , and scorify, as it were, till 
the sulphur has gone ; take out, pour, and the 
result will be a clean button. 

For ores which are much richer in gold 
than silver, and in which it is not desired to 
determine the latter, the operation of inquar- 
tation of the resultant bead can be dispensed 
with by putting in the charge before running 
a piece of pure silver of the proper weight ; it 
will help to collect the gold, moreover. 

Comments on the five preceding processes .— 
With these, as with others, each assayer will 
find some certain one will, with him, work 
better, and give higher results than the oth- 
,ers. He can then practice until he ascertains 
which one suits him the best, and always 
employ that. 





GOLD AND SILVER ORES. 


309 


My own experiments, and those of my stu¬ 
dents, tend to prove that each of the first 
three methods is pretty sure to bring down 
all the gold ; that the fifth method must be 
worked very carefully to obtain correct results, 
and that the fourth is the most unsatisfactory 
of all. Further, that the first method gives 
higher silver than any of the others, which 
supports the theory that, with sulphur in an 
ore during its fusion, oxy-sulphurets are 
formed, which drag silver with them into the 
slag. 

Many ignorant assayers insist that from 
unroasted sulphuret of iron ores, no gold will 
be obtained by crucible fusion. This extra¬ 
ordinary idea, which, however, seems to 
spread, is entirely unfounded, or, at best, is 
based upon botchy experiments. The stu¬ 
dent may rest assured that he can, with care¬ 
ful working, extract all the gold from an 
unroasted ore by any one of the nitre meth¬ 
ods. 




3 IO 


MANUAL OF ASSAYING. 


II. —OXIDE OF IRON. 

One of the results of the decomposition of 
iron pyrites is oxide of iron, existing either as 
limonite, which is the oxide with water, or as 
hematite, the oxide without water. It is even 
more widely distributed than iron pyrites, and 
since the latter is one of the most common 
sources of gold, so likewise is oxide of iron, 
with the advantage that that precious metal 
is retained therein in a free-milling condition. 
It is so universal that any brownish, yellow¬ 
ish, or reddish coating on an ore is almost 
certain to be partially, if not entirely, oxide 
of iron. 

The ore can be treated in two ways, by the 
charge given for the iron pyrites after roast¬ 
ing (on page 299), remembering that there 
is a full part of this ore, against three-fourths 
of a part of the roasted sulphuret, or by 
Aaron’s process. 



GOLD AND SILVER ORES. 


CHARGE.—LITHARGE PROCESS. 

A. T. IVeights. Gramme Weights. Grain Weights. 


Ore. 

... 1 A. T. 

30 

grammes 

480 grains — 1 

Bi-carb. soda “ 

45 

<< 

720 

M 

II 

Carb. potash \ “ 

i 5 

a 

240 

“ = i 

Litharge ... “ 

45 

u 

720 

II 

Silica .. . 

. . . 1 

30 

a 

480 


Borax glass. \ “ 

6 

a 

96 

II 

Charcoal .. . 1 grm. 
Salt cover. 

1 

u 

J 5 i 

u 


The above charge is, for the oxide ore, 
quite free from gangue. As has before been 
stated, diminish the silica and charcoal as the 
gangue increases. 

It may be as well to add a cautionary note, 
to the effect that limonite, the hydrous oxide 
(yellow or brown in color), contains about 
14T per cent, of water of combination, while 
hematite, the red oxide, contains none what¬ 
ever; hence use more charcoal, or other reduc¬ 
ing agent, for the latter than for the former. 







3 1 2 


MANUAL ON ASSAYING. 


charge.— aaron’s process (modified). 

A. T. Weights. Gramme Weights. Grain Weights. 
Ore. i A. T. 30 grammes 48ograins=i oz. 


Bi-carb. soda 

3 

90 

«< 

1,440 “ 

II 

Ut 

Litharge ... 

i “ 

i 5 

u 

240 “ 

>• 

II 

Silica. 

1 

30 

ii 

0 

00 

■'T 

= 1 “ 

Borax glass. 

i “ 

i 5 

u 

24O “ 

= t“ 

Sulphur .... 

i “ 

i 5 

u 

24O “ 

>0 

II 

Flour . 

Iron nails, 6. 

Salt cover. 

A “ 

1 2 

<< 

00 

HI 



Many times the assayer will meet ores 
which are mixtures of iron pyrites, and its 
decomposed substitute, iron oxide. Such 
must be treated by the methods given for the 
former mineral. If the pyrites is in very 
small quantity, Process A, without a prelimi¬ 
nary roasting, may be used (in this case em¬ 
ploy but from one-third to one-half the 
amount of charcoal), as the fluxes will do all 
the necessary desulphurizing. 

III.— SULPHURETS OF COPPER. 

Including sulphuret of copper (chalcocite, 
copper glance, vitreous copper, copper sul- 












GOLD AND SILVER ORES. 


313 


phide), which when pure contains 79.8 per 
cent of copper and 20.2 per cent sulphur, and 
which is more liable to carry silver than gold; 
copper pyrites (chalcopyrite, sulphuret of cop¬ 
per and iron), a valued source of the precious 
metals, and which is composed of about equal 
parts of copper, iron, and sulphur; bornite 
(purple copper ore, variegated copper ore, va¬ 
riegated copper pyrites, erubescite, “ horse¬ 
flesh ” ore, sulphuret of copper and iron), an 
ore similar to the preceding, but with less 
iron; gray copper ore (“fahlerz,” tetrahe- 
drite), a sulphide of copper and antimony with 
smaller and varying amounts of other sulphu- 
rets ; and finally, all other and rarer sulphu- 
rets with copper as an important ingredient, 
such as Barnhardite, Bournonite, Carrollite, 
Covellite, Harrisite, Stromeyerite, and Ten- 
nan tite. 

These ores can be treated by any one of the 
five methods given for the sulphuret of iron, 
and which I repeat here, with some alterations 
in the proportions of the ingredients of the 






MANUAL OF ASSAYING. 


314 

various charges, and, for the sake of space, in 
tabular form. 

Even these charges will have to be modi¬ 
fied more or less to suit any particular sam¬ 
ple, for it may be a mixture of two or more 
of the above-named ores, but they will serve 
as representative methods. Salt cover to all, 
as usual. 



Method 

A. 

Method 

B. 

Method 

c. 

Method 

D. 

Method 

E. 

Ore. 

1 A T. 

30 grms. 
480 grains. 
Roasted. 

1 A. T. 

30 grms. 
480 grains. 

i A. T. 

30 grms. 
480 grains. 

1 A. T. 

30 grms. 
480 grains. 

1 A. T. 

30 grms. 
480 grains. 

Bi-carb. 

Soda. 

1 \ A. T. 

45 grms. 
720 grains. 

i|> A. T. 

45 grms. 
720 grains. 

i-i A. T. 

45~ grms. 
720 grains. 

xi A.T. 

45 grms. 
720 grains. 

3 A. T. 

90 grms. 
i,44ograins. 

Carb. 

Potash. 

i A. T. 

15 grms. 
240 grains. 

| A. T. 

15 grms. 
240 grains. 

1 A. T. 

15 grms. 
240 grains 

i A. T. 

15 grms. 
240 grains. 

O 

Litharge. 

2 A. T. 

60 grms. 
960 grains. 

2 A. T. 

60 grms. 
960 grains. 

6 A. T. 

175 grms. 

2,880 grains. 

2 A. T. 

60 grms. 
960 grains. 

i A. T. 

15 grms. 
240 grains. 

Silica. 

1 A. T. 
grms. 
480 grains. 

x A. T. ‘ 
30 grms. 
480 grains. 

2 A. T. 

60 grms. 
960 grains. 

1 A. T. 

30 grms. 
480 grains. 

1 A. T. 

30 grms. 
480 grains. 

Borax glass. 

\ A. T. 

6 grms. 

96 grains. 

3 A. T. 

6 grms 

96 grains. 

x A. T. 

30 grms. 
480 grains. 

3 A. T. 

6 grms. 

96 grains. 

iA.T. 

15 grms. 
240 grains. 

Charcoal. 

13 grm. 
12^ grains. 

O 

After fusion 
1 grm. 

15^ grains. 

O 

O 

Nitre. 

O 

if A.T. 

50 grms 
770 grains. 

2 ? A. T 

67 grms. 
1,080 grains. 

O 

nr a. t. 

9 grms. 

114 grains. 

Nails. 

O 

O 

O 

6 

6 






























































GOLD AND SILVER ORES. 


315 


Copper pyrites — that is, the sulphurets of 
iron and copper partially oxidized — should 
be treated like the unchanged pyrites. When 
entirely converted into the oxides of copper 
and iron use Method A of the sulphuret of 
copper charge given above, and Aaron’s 
charge on page 312. 

IV.-OXIDES OF COPPER. 

The oxides of copper are the red oxide 
(cuprite), with 88.8 per cent copper, and the 
black (melaconite, tenorite), with 79.8 per 
cent of that metal. As oxidized minerals 
there are the hydrated oxy-carbonates, mala¬ 
chite (green carbonate), and azurite (blue 
carbonate), with 57.4 and 55.3 per cent of 
copper respectively. 

The two oxides differ chiefly in this, that 
the black oxide is oxidizing, i.e., giving up its 
oxygen during fusion, while the other does 
not do so. Hence, extra reducing agent 
must be added to the former. 

Use either the litharge or Aaron’s pro¬ 


cess. 






MANUAL OF ASSAYING. 


3 1 6 

For the former, make up the charge given 
as Method A for sulphurets of copper, using 
g rm - ( I2 ir grains) charcoal for the black 
oxide, and ^ grm. (7-J grains) for the red. 

For Aaron’s process, use the charge on 
page 312. 

Malachite, azurite, and other oxidized ores 
containing not as much copper as the above 
two oxides, will need but the regular amount 
of litharge for the litharge process (i| A. T., 
45 grammes, 720 grains). 

Chrysocolla, the silicate of copper, calls for 
no especial remark, save only that the charge 
will not require quite so much silica. 

V.-GALENA. 

Galena (galenite, “pyrites of lead,” sul- 
phuret or sulphide of lead) is so frequently a 
source of silver, or, at least, so many times 
associated with other minerals that do carry 
silver, that its assay is often called for. Some¬ 
times, although not often, galena is rich in 
gold and quite free from silver; but whether 




GOLD AND SILVER ORES. 


3*7 


auriferous or argentiferous, it makes no differ¬ 
ence in the manner of treatment. 

The silver in this ore varies from a mere 
trace to as high as $1,500 per ton. It is 
claimed that when galena contains over o. 1 
per cent silver, that it is due to the presence 
of a true silver mineral. This is probably so; 
at all events, one can often pick out from the 
cleavage of a rich specimen particles of argen- 
tite or horn-silver. 

For the assay treatment, use Method B, 
p. 289, with the litharge ^ part (meaning by a 
part 1 A. T., 30 grammes or 1 oz) and the 
nitre t 6 q- of a part. Or Method C, with 1 part 
litharge and f part nitre. Or, finally, Method 
D, with \ part litharge. 

An approximate assay for silver in galena 
can be made by cupelling the buttons obtained 
in the lead assay , etc., and making the proper 
calculations, remembering that grammes and 
grains, and not A. T. weights, are used in 
such assays. 



CHAPTER II. 


COPPER ORES. 

Occurrence. —Copper is found both native 
and in combination with many elements, 
principally with sulphur as a sulphide or sul- 
phuret, with oxygen as an oxide, and with 
carbon, hydrogen and oxygen as a hydrated 
carbonate. It has also been discovered asso¬ 
ciated with most of the metals, common or 
rare. 

It is obtained for the arts and manufactures 
mostly from the following ores*. 

1. Native copper (copper, sometimes accom¬ 

panied by silver), when pure, ioo per 
cent. 

2. Cuprite (red oxide of copper), with 88.8 

per cent copper. 

3. Melaconite (black oxide of copper), with 

79.8 per cent copper. 

318 


COPPER ORES. 


319 


4. Azurite (blue carbonate of copper), with 

55.2 per cent copper. 

5. Malachite (green carbonate of copper), 

with 57.4 per cent copper. 

6. Chalcocite (sulphide of copper), with 79.8 

per cent copper. 

7. Chalcopyrite (sulphide of copper and iron), 

with 34.6 per cent copper. 

8. Tetrahedrite (gray copper ore), copper 

variable, normally contains about 38 per 
cent.* 

Assay. —Of the many dry methods for the 
testing of copper ores, it may safely be said 
that no single one is very accurate. The vari¬ 
ous metallurgical works usually have pro¬ 
cesses or modifications of processes peculiar 
to themselves, but which are always more 
or less imperfect. Many of these processes 
are complicated, and require great skill with 
constant practice. 

I have then thought it best to specify but 


* See appendix for more extended list of copper minerals. 




3 2 ° 


MANUAL OF ASSAYING. 


three assay methods, they being representa¬ 
tive ones. 

I. METHOD FOR NATIVE COPPER. 

(As a simple mixture of rock and metallic 
copper.) 

Here the only action is fusion. 

CHARGE. 

Ore.io grammes or 160 grains. 

Bi-carbonate of soda.20 “ “ 320 “ 

Carbonate of potash. 5 “ “ 80 

Borax glass. 1 “ “ 16 “ 

Salt and charcoal cover. 

Sample ore as usual. Mix charge and pour 
in “U ” crucible. Put cover of \ inch salt 
and then 1 inch of wood charcoal. Cover and 
heat intensely for twenty to thirty minutes. 
After cooling, break crucible and clean but¬ 
ton from slag. Divide the weight of button 
obtained by 10 or 160, and multiply this result 
by 100 for percentage of copper. 







COPPER ORES. 


II. METHOD FOR OXIDES AND CARBONATES OF 

COPPER, FREE FROM SULPHUR. 

. 

Here the action is reducing, followed by 
the collection of the copper globules into one 
button. 

CHARGE. 

Ore.io grammes or 160 grains. 


Black flux substitute . .. 

. .30 

(< 

00 

0 

•s 

Borax glass. 

•• 5 

u 

“ 80 “ 

Argol. 


t( 

“ 3 2 

Salt and charcoal cover. 





Use a “ U ” crucible, chalk-lined. Cover, 
heat gradually for twenty minutes, then 
increase to white-heat for forty minutes. Re¬ 
move, tap, and let cool. Results approximate, 
the error augmenting by the presence of other 
metals. 

HI. METHOD FOR SULPHIDES OF COPPER, WITH 
ARSENIC, ANTIMONY, LEAD, MERCURY, ZINC, 
ETC. 

The first step, concentration, is to bring 
down into a matte all the copper, and to get 
rid of obnoxious lime or baryta gangues. 






32 2 MANUAL OF ASSA VING. 


CHARGE. 

Ore, according to 


richness. to to 30 grms., or 160 to 480 grains. 

*Iron pyrites .... 2 “ 6 “ “ 32 “ 96 “ 

Borax glass. 8 “ 24 “ “ 128 “ 384 “ 

Salt cover. 


Mix as usual and transfer to crucible. If 
lead is present, put in a couple of nails. Fuse 
in hot fire, remove when finished, take out 
nails if any have been used, cool, break away 
the slag from the matte, and treat the latter 
as follows : 

The second step, roasting, is to expel the 
sulphur and the volatile metals, arsenic, anti¬ 
mony, zinc, or mercury, converting the copper 
into an oxide. Great care must be employed 
here, hence observe the directions pdven U n- 

c> 

der Roasting in the crucible process for gold 
and silver ores, pages 273 to 278, using coke 
in place of charcoal, and no silica. 

I he third step is reduction, or bringing the 
copper from its state of oxide to that of a metal. 


* Containing no copper; test with nitric acid and ammonia. If 
pyrites is in the ore to any extent, no extra amount need be added. 






COPPER ORES. 


323 


CHARGE. 


Ore (roasted).... . 

. .30 grammes or 480 grains 

Black flux substitute.. 

.. .90 

«< 

“ 1 A Ar\ << 

1 , 44 ° 

Borax glass. 

...15 

u 

“ 240 

Lime glass. 

7 i 

ll 

“ 120 “ 

Red oxide iron. 

Salt cover. 

••• 3 

il 

“ 48 “ 


(If 10 grammes or 160 grains ore is used, 
reduce the above quantities two-thirds.) 

Mix the ore, oxide iron, and one-third the 
black flux substitute, transfer to the crucible, 
settle down, then add the remaining two-thirds 
of the black flux substitute, the borax glass, 
lime glass, and common salt, in consecutive 
layers, and on top of all a piece of coal about 
the size of a hazel nut. Heat slowly at first, 
then intensely, remove, cool, detach button, 
etc. If it seems red and pure and is malle- . 
able, weigh and calculate percentage. If not, 
then there comes the fourth step, purification 
or refining. 

Two large cupels are well heated in the 
muffle; into each a piece of pure lead 3 










324 


MANUAL OF ASSA YING. 


grammes or 48 grains is placed, and the 
muffle is closed. When the leads have melt¬ 
ed, open the door, and into one cupel drop 
the impure button, into the other a piece of 
pure copper of the same weight. Let them 
remain till “brightening” occurs, indicated by 
a peculiar green color. As soon as this has 
happened, cover cupels with coke or coal 
dust, take out and cool in water. The loss 
the pure copper has sustained in cupellation 
is supposed to be the same as the button 
loses, and is to be added to that of the latter. 
Weigh and calculate on first weight of ore 
taken. Results moderately accurate. 

Read Mitchell, and Bodeman and Kerl on 
copper assays.* 

* Several criticisms have been made upon this chapter to the 
effect that it is altogether too brief. I have made no endeavor to 
extend it in this revised edition, for the reasons (one of which has 
been previously stated) that the fire processes are not accurate, and 
that they are gradually being substituted everywhere by the more 
exact volumetric and electrolytic methods which I describe in full 
detail in the appendix. The dry assay methods described are as 
good as any, and cover the three classes of copper ores common 
to this country, i.e., free metal, oxidized, and sulphuretted ores. 






CHAPTER III. 

LEAD ORES. 


Occurrence. —Lead is very rarely found 
native (that is, as the pure metal), but occurs 
combined with various elements, as antimony, 
arsenic, carbon, chlorine, chromium, molyb¬ 
denum, oxygen, phosphorus, selenium, sul¬ 
phur, tellurium, tungsten, vanadium, etc. 
Combinations of some of the above elements 
with each other and with lead exist, either 
alone or associated with such metals as cobalt, 
copper, gold, iron, mercury, nickel, silver, 
zinc, etc. 

Many of these compounds are merely min- 
eralogical curiosities, and will not be consid¬ 
ered here. 

The important workable ores are the fol¬ 
lowing : 

i. Galenite (galena, sulphide or sulphuret of 
lead), when p2ire consisting of 86.61 per 

cent lead and 13.39 per cent sulphur. 

325 



326 


MANUAL OF ASSAYING. 


2. Cerussite (white lead ore, carbonate of 

lead), containing 77.52 per cent lead. 

3. Minium (red oxide), with 90.80 per cent 

lead.* 

Assay. —The method of assaying a lead 
ore depends upon the nature of the ore. 

I. METHODS FOR GALENA. 

(Also for selenides, sulphates, and for galena 
containing antimony and arsenic.) 

A. By Crucible Fusion in Furnace. 

1. With bi-carbonate of soda and metallic 
iron. 

CHARGE. 

Ore. 10 grammes, or 160 grains. 

Bi-carbonate of soda.25 11 “ 400 “ 

Carbonate of potash.10 “ “ 160 “ 

3 iron nails or 
3 loops of iron wire. 

Salt cover. 

Prepare the sample according to the direc¬ 
tions given on pp. 185-191. 


* For more complete list of lead minerals see appendix. 







LEAD ORES. 


327 


Weigh first the carbonates, then the finely 
pulverized ore, and mix thoroughly on glazed 
paper. 

(Read the notes on the “ Crucible Assay of 
Gold and Silver Ores/’ pp. 257-258.) 

Brush into a lettered or numbered small 
sand crucible (size “ U ” of Battersea make), 
and settle contents down. 

If there is considerable pyrites in the ore, 
sprinkle now over the surface of the charge 
one gramme of finely powdered borax glass. 

The three iron nails (eight-penny) are to 
be held together by their heads with iron wire 
(No. 16), and then inserted, points down, in 
the crucible, leaving a loop of the wire hang¬ 
ing over the edge that the nails may be easily 
and quickly withdrawn when the operation is 
concluded. If wire only is used, bend a piece 
of the No. 16, about six inches in length, in 
the form of a horse-shoe with a loop above, 
and in the loop hang two smaller pieces bent 
in the form of hair-pins ; let all six points be 
about on a level. Insert into the charge. 




MANUAL OF ASSAYING. 


328 

Finally pack on the surface of the charge 
and around the nails or wire one-half inch of 
dry salt. 

Place the crucible in a moderately hot fire, 
cover and surround with coke. 

This process will require twelve to four¬ 
teen minutes. 

When fusion is complete, take off the cover, 
remove crucible from fire, then by means of 
small tongs stir the nails or wire loops around 
in the molten mass once or twice, and while 
in the hot fluid tap them against the side of 
the crucible, then withdraw them, tap gently 
the crucible and cover. All this should be 
done as rapidly as possible. 

When cold, break and hammer lead into 
shape as usual. 

The weight of the button, multiplied by ten 
(or divided by sixteen and multiplied by ten), 
gives the ore’s percentage of metallic lead. 

Tests of Good Work .—After fusion the 
interior of the crucible should be smooth and 

% 

have no half-fused portions adhering to the 




LEAD ORES. 


329 


sides. The charge should be well settled to 
the bottom and have an even surface. The 
slag should be uniform in character, and of a 
purplish-black color. The lead should be at 
the bottom in one button, and be perfectly 
malleable. A glistening button indicates 
undecomposed galena ; a brittle one the pres¬ 
ence of antimony, arsenic or iron. 

The alkaline carbonates act mainly as 
fluxes, but a portion of the lead they convert 
into a double sulphide of lead and soda (or 
potash), which the iron desulphurizes, form¬ 
ing sulphide of iron and metallic lead. 

In order to learn the proper running of this 
lead assay, it will be well for the student to 
perform it at least ten times on the same ore. 

2. With black flux substitute and metallic 
iron. 

CHARGE 

Ore. 10 grammes or 160 grains. 

Black flux substitute.35 “ “ 560 “ 

3 iron nails or 
3 loops of iron wire. 

Salt cover. 





330 MANUAL OF ASSA TING. 

Treat in same manner as for the first 
method. Let remain in fire twelve or thirteen 
minutes. 

Add one gramme or fifteen and one-half 
grains of borax glass to pyritic ores. 

The carbon of the flour of the black flux 
substitute exerts an additional reducing action. 

Perform this assay a number of times for 
practice. 

The remarks given under the first method 
are applicable here. 

3. With cyanide of potash. 

Ore. 

Cyanide of potash 
Salt cover. 

Use a “D” Battersea crucible. Ram into 
the bottom of the crucible 10 grammes cyan¬ 
ide, above this pour on the charge, cover first 
with 5 grammes cyanide, lastly the salt. 
Time, 14-15 minutes, low red heat, 5 minutes 
at slightly higher temperature. 


CHARGE. 

_ 10 grammes or 160 grains. 

.-_. 30 u “ 480 “ 







LEAD ORES. 


33 [ 


Half-a-dozen runnings will be sufficient for 
this method. 

These three methods can be performed 
with satisfaction in Fletcher’s gas furnace 

(P- 74 > 


B. By Crucible Fusion in Muffle. 

4. With bi-carbonate of soda and argol. 


Ore.. 

Bi-carbonate of soda 
Carbonate of potash 

Argol. 

Flour. 

Borax glass. 

2 loops of iron wire. 


CHARGE. 

.10 grammes or 160 grains. 

.15 “ “ 240 “ 

.10 “160 “ 

. 7 “ “ 112 “ 

. 5 “ “ 80 “ 

.3 “ “ 48 “ 


Salt cover. 

Mix the ore, soda, argol and Hour, and pour 
into a small sand crucible large enough to 
stand in the muffle used. Sprinkle over the 
charge the fine borax glass, insert two pieces 
of iron wire bent as hair-pins, and tamp down 
with from 4 to ^ inch dry salt. Use no cover. 

Have the muffle at a bright red heat, and 
place the crucible or crucibles therein ; after 










MANUAL OF ASSAYING. 


about ten minutes of good heat, increase the 
temperature for twenty-five minutes longer, 
when the contents of the crucibles should be 
in perfect fusion. 

Take out, remove wires, tap, and let stand 
covered till cool, do not pour, break, hammer 
button, etc. 

The size of the crucibles used will depend 
upon the height of the interior of the muffle, 
and the fact that the muffles usually employed 
are small very often either necessitates a 
smaller charge, or renders it impossible to use 
this process. 

For this work, one may either use the very 
small crucibles of the ordinary form, surround¬ 
ing each crucible with a little cup or platform 
of fire-clay and sand mixed up with borax 
water, that it may stand securely in the muffle, 
or the special form for muffle fusions shown 
in fig. 73. The latter is recommended. 

C. By Fusion in Scorifiers. 

This is a modification of the lead assay 



LEAD ORES. 


333 


designed to be used where the muffles are not 
large enough to admit of crucibles. 

It is simply a substitution of scoriners for 
crucibles, using the same charges (reduced 
one-half in quantity) as for crucible work, 
and employing the muffle. 

Half the third charge works well, thus : 

5. With cyanide of potash. 

CHARGE. 

Ore. 5 grammes or 80 grains 

Cyanide of potash.15 “ “ 240 

Salt cover. 

For a “J” Battersea muffle, employ a 3^ 
inch Battersea scorifier. Have the muffle red 
hot, introduce scorifier, cover with 3J inch 
circular crucible cover (“ G ” of Battersea), 
heat moderately for ten minutes, then in¬ 
tensely for twenty. Remove cover, take out 
scorifier, do not pour but let cool covered, 
break, and shape lead button. Multiply 
weight by twenty (when grammes are used), 
or divide it by eight and multiply the quotient 
by ten (when grains are used) for percentage. 





334 


MANUAL OF ASSA YING. 


Comparison of Processes .—The cyanide of 
potash process in crucibles gives the highest 
results, the buttons are clean and malleable, 
and the slags almost always uniform. I have 
found it the one most quickly learned, and so, 
on all accounts, I give it the preference. 

The fourth process (crucible in muffle) 
comes next in percentage of lead obtained. 

The second process (black flux substitute) 
ranges next, and is quite satisfactory to work. 

Very close in results to the preceding, is 
the third process in scoriflers (No. 5, half 
charge). 

The first process (bi-carbonate of soda) 
gives lower results than any of the others. 

A method with ferrocyanide of potash, that 
is sometimes used, I have omitted entirely, on 
account of its inaccuracy. 

II. METHODS FOR OXIDES AND CARBONATES. 

(Cerussite, minium, etc.) 

By crucible fusion in or out of muffle. 

6. With soda, potash and argol. 




LEAD ORES. 


335 


CHARGE. 

Ore.io grammes or 160 grains. 

Bi-carbonate of soda.15 “ “ 240 “ 

Carbonate of potash. 5 “ “ 80 

Argol. 5 “ “ 80 “ 

Salt cover. 

Mix as usual, and transfer to small crucible. 
Cover, if fusion is made in the open fire, but 
not if the muffle is used. Heat gradually for 
about fifteen minutes, then somewhat more 
strongly till fusion ensues. Take out, pour 
or not, as desired. Cover if left in crucible 
to cool. 

Action reducing—the oxygen of the ore is 
seized by the carbon of the argol, leaving 
metallic lead. 

7. With soda, argol and borax. 

Prepare a flux, in quantity, of the following 
ingredients : 

CHARGE. 

2 parts bi-carbonate of soda. 

2 parts argol. 

1 part common borax, in powder. 

1 part flour. 








336 


MANUAL OF ASS A TING. 


Have the above well mixed, then sifted, and 
keep ready for use. 

Fill about two-thirds full a so-called “5 
gramme” crucible (page 112), with the above 
flux, add 5 grammes, or 80 grains, of the ore, 
and mix in crucible. Put in muffle without 
cover. Keep the heat as low as possible, 
without letting it get too cold. 

If the ore shows sulphurets, put in a nail or 
two. 

If the ore is quite calcic or barytic, make 
the borax 1 y 2 parts and the flour ^ of a part. 

For ores containing much manganese, add 
to flux a little more borax and flour. 

8. With cyanide of potash. 

CHARGE. 

Ore.... . 5 grammes or 80 grains. 

Cyanide of potash. 30 “ “ 480 « 

Salt cover. 

Mix as for charge 3 on page 330. 

Fuse at low heat for 20 minutes, then end 
with higher heat for 5 minutes. Make sure 
that all bubbling ceases. 





LEAD ORES . 


337 


Concluding Remarks .—At the best, the assay 
of lead ores is inaccurate, mainly on account 
of the volatility of the lead itself, though in 
the case of galenite ores, it is supposed that 
the galena begins to sublime before the de¬ 
composition is effected. 

Also, the lead button is liable to contain 
antimony, iron, and zinc from the ore, or iron 
from the nails, wire, or iron salts employed in 
the assay. 

Try then to avoid an unnecessarily high 
heat, remove assays as soon as fusion is ob¬ 
tained, and use covers as much as possible. 

The latest investigations on the fire assay of 
lead tend to demonstrate that cyanide of 
potash is the best reducing flux for all the ores 
of lead, (corroborating the remarks on page 
334,) not only for the sulphides, oxides and 
carbonates, but for the rarer minerals, as the 
sulphate (anglesite), the phosphate (pyromor- 
phite) and others. A final note of caution is 
to the effect that the greater the amounts of 
reducible metals a lead ore contains (such as 




338 


MANUAL OF ASSAYING. 


copper, arsenic, antimony, etc.) the greater 
the error. These elements may predominate 
to such an extent as to make the fire methods 
inapplicable. For while there may be a com¬ 
pensation of errors (the loss of lead by volatil¬ 
ization counteracted by the addition of the re¬ 
duced metals), yet too much uncertainty as to 
the results would make them practically 
worthless. 





APPENDIX. 














































































SECTION I. 


SPECIAL METHODS. 

I. ASSAYING OF THE VARIOUS MINERALS CON¬ 
TAINED IN AN ORE. 

It is sometimes desirable to know where the 
gold and silver are located in an ore, that is, 
which minerals carry them to the greater 
extent. This can not always be done, for the 
various minerals may be so thoroughly com¬ 
mingled that separation will be impossible. 
But in other cases, it can be done with suc¬ 
cess. For example, an ore is found to be 
made up of three distinct minerals, blende, 
galena and pyrites in a quartz gangue. Weigh 
the piece selected, and crush roughly in a 
tnortar, taking care not to lose any, and pour 
out on a clean surface, as a sheet of white 
paper. With a pair of pincers pick out such 

pieces of the quartz as show none of the min- 

341 


342 


MANUAL OF ASSA YING. 


erals mentioned, and reject them. Then it 
will be comparatively easy to put aside, in 
three piles, the minerals, each quite free from 
the other two. By carefully crushing the 
remaining mixed pieces, the entire lump will 
finally be separated into its three component 
valuable minerals and the worthless gangue. 

Weigh each lot, and assay the whole of. 
each or fractions thereof. 

To show method of calculation, I give the 
following 

Example. 

Weight of sample of ore, 500 grammes, 

Which was composed of: 

Pyrites, 40 grammes. 

Blende, 60 “ 

Galena, 100 “ 

Quartz gangue, 300 “ 

• 5°° grammes. 

Percentage of pyrites= T Yo X 100= 8 

“ “ blende = ^ 6 / ¥ X 100= 12 

“ “ galena 100= 20 

“ “ quartz = |-2-^X 100= 60 


100 




APPENDIX. 


* \ A 

Pyrites.—The 40 grms gave 10 mgrms gold—no silver: 

X 29.166=0.58332 of an ounce per ton. 

Blende.— 10 grms gave 4 mgrms silver—no gold: 4X6 
= 24; ^0X29.166=1.39 oz. silver per ton. 

Galena.— 20 grms gave 160 mgrms silver—trace of gold: 
160X5 = 800; 1^^X29.166 = 46.6 oz. silver per ton. 

II. ASSAYING OF ORES CONTAINING FREE GOLD 

OR FREE SILVER. 

The average ore does not carry the precious 
metals in the free state. But when they are 
present in such form, proceed as follows: 

Crush the sample selected, having first 
weighed it. Pulverize as usual, and sift, 
using the box sieve. As a result we shall 
have two things, the finely powdered siftings 
below and more or less free metal in scales 
on the sieve. 

Weigh the scales, and, as a check, the sift¬ 
ings. The weight of the latter should be but 
a trifle less than the difference between the 
original weight and that of the scales, if care 

o o 

has been taken in pulverizing. 

If not too large an amount, all the scales 



344 


MANUAL OF ASSA YING. 


should be wrapped in pure lead-foil, and 
cupelled directly. If quite an amount be 
present, simply scorify down in the usual 
manner. 

Take a weighed fraction (one-half, one- 
tenth, one-twentieth, as the case may be ) of 
the siftings, and assay by scorification or cru¬ 
cible process. The number of milligrammes 
ofold and silver obtained are each to be multi- 
plied by the proper fraction to ascertain the 
amounts present in the entire bulk of the 
siftings. Add the gold thus calculated to be 
in the whole of the siftings to the amount 
found to be in the scales, and the same with 
the silver. If the metal is all free gold or all 
free silver, the calculations are still simpler. 

The following example explains itself, and 
illustrates the methods of calculation. Fac¬ 
tors, depending upon the relation of the assay 
ton of 29.166 grammes to the amount of sam¬ 
ple taken, may or may not be used, as desired. 
If a fixed quantity of ore, as 100 grammes, is 
always taken, the factors of 29.166-f- too — 




APPENDIX. 


345 


0.29166, or of 100 4- 29.166 = 3.428, will, of 
course, always be constant. 


Total weight of sample is.. .320.000 grammes 

Of which the scales weighed.260 

Hence the siftings weighed.319.740 

Factors.29.166-5-320= 0.09114, 

Or .320-^29.166 = 10.97102. 

208 mgrms. silver, 

Scales: the 0.260 grms. produced .. -< 9 - 1 


217.1 


gold, 

total. 


208-^320=0.65 ; 
then 0.65X29.166, 
or 208X0.09114, 
or 208-7-10.97102, 
0.1-4-320=0.0284375 ; 

then 0.0284375X29.166, 
or 9.1X0.09114, 
or 9.1-7-10.97102, 


= i8.95=oz. silver per ton of scales. 


=o.83 = oz. gold per ton of scales. 


Siftings : 319.74 grammes, 

30 grammes produced 


\ 51.75 mgrms. silver, 
\ 1.50 “ gold, 

[52.25 “ total. 


51-75-5-30=1.725; 1.725x319-74=551-5515; 551-5515-5-320= 


1.7236; 

then 1.7236X29.166, 
or 551.5515XO.09114, 
or 551-5515-5-10.97102, 


= 50.2=oz. silver per ton of 

► 

siftings. 


1.50-7-30=0.05 ; 0.05X319-74= 1 5 - 9 s 7 , 
15.987-7-320 = 0.04996 ; 

















MANUAL OF ASS A YING. 





then 0.04906X29.166, 
or 15.987X0.09114, 
or 15.987-MO.97102, 


► = i.45=oz. gold per ton of siftings. 


Silver : in scales, 1S.95 oz., @ $1.29 per oz., =$24.44 per ton. 
“ siftings, 50.20 “ “ “ “ = 64.75 


total, 69.15 “ “ “ “ =$89.19 


Gold: in scales, 0.83 oz., @$20.67 per oz., = $17.15 per ton. 
“ siftings, 1.45 “ .. = 29.97 

“ total, 2.28 “ “ “ “ =$47.12 “ 


Total value of scales ... $24.44+$i7.i5=$ 41.60 per ton. 
Total value of siftings .. .$64.75-1-^29.97=$ 94.72 
Total value of ore.$89.i9~(-$47.i2=$i36.3i 


Check.* 

0.260: 208:: 29.166: x, o. 26 ox = 29.166X208 = 6066.928, x 
=6066.928-4-0.260=23334.338,23334.338X1.29 = 30101.29. 
0.260 : 9.1:: 29.166 : x, o 26ox = 29.i66X9.i = 265.4io6, x 
= 265.4106-4-0.260=1020 81, 1020.81 X20.67 = 2i 100 14 

30101.294-21100.14=51201 43. 


0.260 tons scales, @ $51,201.44 per ton = $i3,3i2.37 
319.740 “ siftings, “ 94.72 “ = 30,285.77 

320 tons original ore, worth $43,598.14 ; or 

1 ton is worth $136 24. 


*The idea of the check or verification is taken from C. H. 
Aaron’s excellent little work on assaying, and consists in consid¬ 
ering the ore as made up of two kinds of material, assaying each 
part as though it was the original ore, and from the number of 
imaginary tons of each kind, calculating the actual value of a ton 
of the mixed or original ore. 














APPENDIX. 


347 


III. ANALYSIS OF COPPER ORES. 

The wet process or analysis of copper ores 
is so much more accurate than the dry pro¬ 
cess or assay, that it should always be 
employed when practicable. 

As in the assay of copper, so in the anal¬ 
ysis, there are many methods, here included 
under three heads ; volumetry, gravimetry 
and electrolysis. While there are good ways 
of determination among the first two classes, 
yet I prefer one in the third, owing to its 
simplicity, accuracy, freedom from intricate 
calculation, and the ease with which it can be 
acquired. 

The process I now describe is known as the 
Luckow method, and consists, briefly defined, 
in dissolving the copper out of its combina¬ 
tions by means of acids, and then depositing 
it as the metal itself upon another metal, 
platinum, by the action of an electric current. 

It makes no difference whatever in this 
method, how the copper is originally com¬ 
bined, whether as a sulphide or in a mixture 



348 


MANUAL OF ASSAYING. 


of sulphides of other metals, an oxide or car¬ 
bonate, a matte or an alloy; the copper 
comes out as metallic copper in any case. * 

PROCESS. 

Prepare the sample in the usual manner, 
being sure to use a ioo-mesh sieve. Sample 
and weigh out very carefully on the ore scales, 
one gramme, if the ore be at all rich (say 
above 20 per cent), or five grammes if it be 
poor in copper (below 20 per cent). 

Brush into a casserole, i.e., a porcelain 
evaporating dish with a handle (fig. 91), and 
cover with a clock-glass (fig. 84), of slightly 
larger dimensions, and add 10 cubic centi¬ 
metres of pure and concentrated nitric acid, 
by means of a 10 c.c. pipette (fig. 92). 

Now place the casserole either on a sand- 
bath (a common tin plate holding some dry 

* If accessible, consult a very interesting paper, entitled “Com¬ 
parison of Various Methods of Copper Analysis,” by Mr. W. E. C. 
Eustis of Boston, which was read at the August, 1882, meeting in 
Colorado of the American Institute of Mining Engineers, and is 
to be found among the published transactions of that society 




APPENDIX. 


349 


sand), or on a piece of wire gauze, supporting 
either on a ring-stand (fig. 97), and heat with 
a Bunsen burner (fig. 99), or alcohol lamp. 
Continue this heating some little time, then 
let cool. When cold, add, from another 
pipette, 5 c.c. of pure and concentrated sul¬ 
phuric acid, and heat to boiling till no more 
red fumes are given off, but in their stead 
dense white vapors are delivered. 

The red fumes are from the nitric acid, the 
excess of which we wish to get rid of, which 
is done by means of the sulphuric acid, and 
the white fumes show that the former acid is 
about gone. Let the casserole stand till cold. 

Now add about 50 c.c. of distilled water, 
stir with a glass stirring rod, heat, and let 
stand till any undissolved matters have set¬ 
tled to the bottom of the casserole. 

While this is doing, prepare for filtering, 
that is the separating of the dissolved copper 
(and other metals) from the undissolved 
silica, etc. Place in proper position a filter- 
stand (fig. 121), glass funnel (fig. 90), and 



35 ° 


MANUAL OF ASSAYING. 


glass beaker (fig. 89). The filter-paper is 
fitted by cutting a piece in a square, then 
folding in half, diagonally, and then into quar¬ 
ters ; it will form a triangular figure, and if the 
corners are cut off in a curved line, a circle 
will be formed on spreading out. Upon open¬ 
ing the folded paper so that three thicknesses 
come on one side and one on the other, a 
filter is obtained, which is placed in the funnel 
and wetted by means of the wash-bottle (fig. 
83). This useful piece of apparatus is oper¬ 
ated by simply blowing in at a ; a fine stream 
of water at once issues from b, which can be 
directed against any part of the funnel. 

Filter the liquid in the casserole by holding 
the glass-rod outside the lip of the vessel, 
allowing the solution to run down the rod 
into the funnel, till the latter is nearly full. 
Repeat the operation until nearly all the solu¬ 
tion has passed through the funnel, and only 
the sediment, nearly dry, is left in the casserole. 
Examine the residue, and if it is dark-colored, 
it is best to repeat the treatment with acids. 




APPENDIX. 


35 1 


Generally, however, once is enough. Finally 
wash the contents of the casserole into the 
funnel, which fill three or four times with 
water, which will be sufficient to wash out all 
the copper solution. 

The residue on the filter-paper consists of 
silica and other substances insoluble in the 
acids used. It should contain no copper. 

The filtrate, that is the filtered liquid, con¬ 
tains the copper as sulphate (with perhaps 
some nitrate), also it may be, iron, lead, etc., 
but these do no harm. 

The next thing is to deposit the copper 
upon platinum. We may use a vessel entirely 
of platinum, or a copper dish lined with plati¬ 
num, or a horseshoe shaped strip of platinum 
suspended in a glass beaker. In case the 
operator possesses the platinum or platinum- 
lined dish, clean it thoroughly by washing. If 
it is a new vessel, best rinse it first with some 
solution of caustic soda or potash to remove 
grease, then rub it gently with a little fine 
sand, thus giving the interior a surface favor- 



35 2 


MANUAL OF ASSA YING. 


able for deposition. Be sure to wash off all 
the soda or potash solution and sand, then 
warm till it is perfectly dry. When cool, 
weigh carefully on the ore scales and note 
the weight. Pour the copper solution into 
the platinum dish, using the glass-rod, which 
rinse off with water into the dish; finally rinse 
out the beaker with a little water into the 
dish. 

We now have a weighed dish containing 
copper in solution from a known weight of 
ore. It remains to connect it with a battery, 
which latter is now described. 



Fig. 130 represents two cells of what is com¬ 
monly known as the “ Bunsen Carbon,” which 

















































APPENDIX. 


form a battery powerful enough for our pur¬ 
pose. A quart size will be about right. It 
consists of a glass cell or jar to contain the 
dilute sulphuric acid, a cylinder of cast-zinc, 
of which the ends do not quite meet ; a po¬ 
rous earthenware cup, to hold nitric acid, and 
a rod of compressed carbon. 

Prepare a mixture of strong sulphuric acid 
(ordinary commercial) and water in the pro¬ 
portion of one part of the former to ten of the 
latter, observing the precaution of pouring the 
acid into the water, never the reverse. Let 
the zincs stand in this acid solution for two or 
three minutes, then pour over them a little 
mercury, and rub with a piece of soft rag tied 
around a stick, till the entire surface, inner 
and outer, of the zincs, is coated with amal¬ 
gam. 

Put each cell properly together and fill the 
glass jars with the sulphuric acid mixture, just 
covering the tops of the zincs. Next, nearly 
fill the porous cells with concentrated (com- 





354 


MANUAL OF ASS A YING. 


mercial) nitric acid. * See that the binding 
screws are filed bright, also the connecting 
wires, to make good contact. Arrange appa¬ 
ratus as follows : 

The zinc of the first cell is to be united 
with the platinum dish by means of a coil of 
copper wire underneath the latter. A strip of 
platinum foil (cleaned with potash solution 
and sand) just dips into the solution of cop¬ 
per, and is connected to the carbon of the 
second cell by a copper wire. Another wire 
between the zinc of this latter cell and the 
carbon of the first, completes the circuit. 
Cover the dish with two pieces of window- 
glass, to prevent loss by spattering. 

The copper at once begins to line the inte¬ 
rior of the dish, and in from four to six hours 
the deposition will generally be complete. 
Time is often gained by starting the action at 
evening, and letting it run all night. 

Prove the complete deposition of the cop- 

* A bench of from two to six so-called “gravity” cells will do 
instead of the pair of Bunsen Carbons, and are more constant. 



APPENDIX. 


355 


per by taking one drop of the solution and 
adding to it one drop of sulphuretted hydro¬ 
gen water, mixing the two on a white surface 
(cover of a porcelain capsule). If no colora¬ 
tion ensues, the copper has all been thrown 
down ; if a black discoloration follows, then 
there is still copper in solution. In this latter 
case, continue the current till the test is 
negative. 

In the former case, pour the contents of the 
dish into a clean beaker, rinse the dish, the 
under surfaces of the glass plates and the 
platinum strip, into the same beaker. On 
adding - to the contents of this beaker an 

O 

excess of aqua ammonia, no blue coloration 
should be seen. 

Add a few drops of alcohol to the dish, 
rinse around and drain off. Set fire to the 
little remaining in the dish, and when the lat¬ 
ter is cool, weigh. The difference between 
this latter weight and the original weight of 
the dish is metallic copper. I give an 
example : 




356 


MANUAL OF ASSAYING. 


Weight of ore takers i gramme. 

Grammes. 

Weight of platinum dish and copper = 56.4o8 
“ “ “ “ empty = 55.659 

“ “ copper from i gramme^ 0.749 

0.749 multiplied by 100, gives 74.9 per cent 
of metallic copper in the ore. 

As before mentioned, instead of the platinum 
dish, which is quite expensive, a glass beaker 
can be used to contain the copper solution. 
A second platinum strip, on which is to be 
deposited the copper, must be used here. 
Dip this in the beaker and connect with a 
zinc element. The platinum strip in straight 
form connects with the other carbon as usual. 

If the copper should form dark colored on 
the platinum, it is because the solution is too 
acid. Nearly neutralize with a little ammo¬ 
nia water, to counteract its bad effect. Too 
strong a current should also be avoided. I 
have given this process well in detail, but it 
will be found to be much easier learned than 
described. It is a very pretty and satisfactory 
method. 




APPENDIX. 


357 


Volumetric analysis of copper ores. 

If very many tests of copper ores, slags, 
mattes, etc., are to be made daily, it will be 
better to use the volumetric process, for while 
it is not quite so accurate as the battery pro¬ 
cess just described, it is much more rapid. 

My thanks are hereby tendered to Mr. F. 
E. Fielding, of Virginia City, Nev., for many 
of the details embodied in the following de¬ 
scription. 

Preparation of standard sohitions. 

Solution of cya?iide of potassium. —Dissolve 
13°. 2 grammes of the pure salt in i litre 
(i,ooo c.c.) of distilled water, and preserve 
from the light in a glass-stoppered bottle. 

Solzction of metallic copper. — Dissolve i 
gramme of pure copper in 25 c.c. nitric acid 
of 32 0 Beaume (specific gravity 1.26, see page 
2 11) in a covered beaker; then add 7 c.c. of 
dilute sulphuric acid. When dissolved and 
cool add caustic ammonia, or, better still, am¬ 
monium carbonate, in slight excess, or until 
the blue color is perceptible throughout. Di- 





35 « 


MANUAL OF ASSAYING. 


lute, when cool, with distilled water to exactly 
i litre. 

Standardizing the cyanide solution .— Divide 
the copper solution in two beakers, so that 
exactly 500 c.c. shall be in each one, repre¬ 
senting \ gramme of pure copper. Run in 
the cyanide solution from a burette until a 
faint violet color is produced. Treat the sec¬ 
ond portion in the same manner, and take the 
mean of the two results as the standard. 
Multiply each result by two to bring it up to 
the basis of 1 gramme of pure copper, repre¬ 
senting 100 per cent. The cyanide solution 
should be re-standardized every day or so. 

Preparation of the ore solution. 

Weigh 2 grammes of the ore, or 5 grammes 
if very poor in copper, place in a flask, beaker, 
or casserole, moisten with about 7 c.c. sul¬ 
phuric acid, then add 25 c.c. of nitric acid. 
Digest at a gentle heat, or until the silicates 
look white, showing that all the metals have 
been extracted. Boil until fumes of nitrous 
acid are no longer evolved, cool, and add am- 





APPENDIX . 


359 


monia or carbonate of ammonia in slight ex¬ 
cess ; allow the solution to become cool and 
the separated flakes of brown-red hydrated 
sesquioxide of iron (if present) to settle to 
the bottom of the vessel. If necessary, filter, 
and wash the filter paper thoroughly. 

The analysis. 

The standard solution of cyanide is now 
gradually added from the burette (constantly 
stirring the copper solution), until the blue 
color has entirely disappeared, and has been 
replaced by a faint violet tint, corresponding 
as nearly as possible to the shade produced in 
titrating the solution of pure copper in stand¬ 
ardizing the cyanide solution. The number of 
c.c. used to produce this is now read off, and 
from it the percentage of copper in the ore is 
calculated. A single example will illustrate 
the simplicity of the calculations. 

We will imagine it required 125 c.c. of the 
cyanide solution to neutralize the 1 gramme 
of pure copper representing 100 per cent., 





360 


MANUAL OF ASS A Y1NG. 


while it took but 75 c.c. for, say, 2 grammes 
of ore. 

125 x 2 = 250 ; 75-7-250=0.30 ; 0.30 x 100=30, or 30 per cent. 

Hence the rule : Multiply the number of 
c.c. of cyanide solution used for the pure cop¬ 
per test by the number of grammes of ore 
taken. Divide the product into the number 
of c.c. employed on the ore test, and the quo¬ 
tient multiplied by 100 will give the percentage 
of copper in the ore. 

When a sulphuretted ore is to be operated 
upon, it will, in a majority of cases, be com¬ 
pletely oxidized by a mixture of sulphuric 
and nitric acids, but should any globules of 
sulphur remain, they may be taken out after 
the dilution of the solution, ignited, and the 
residue dissolved by nitric acid, and added to 
the original solution. (Or such ores may pre¬ 
viously be roasted in the manner described in 
the section on gold and silver ores.) Some 
ores are best attacked by aqua regia (i part 
nitric acid to three parts hydrochloric acid). 

Owing to the influence of varying quanti- 





APPENDIX . 


3 61 


ties of ammonia and of ammonium salts upon 
the decolorization of copper solutions by po¬ 
tassium cyanide, it is necessary that both the 
test solution originally prepared and the vari¬ 
ous copper solutions subsequently titrated 
should contain, as nearly as possible, equal 
amounts of ammonia. 

Interferences , and their removal. 

Zinc, nickel, arid cobalt. —These, if present, 
render the analyses unreliable, so that, in such 
cases, the copper must be removed by precipi¬ 
tation from its solution. This may be done 
by placing a piece of iron or zinc in the solu¬ 
tion — care being taken that nitric acid is not 
present. The precipitated metallic copper 
thus obtained is, after removal from the re¬ 
maining solution of interfering metals, dis¬ 
solved in the usual manner.* The copper 
may also be precipitated as sulphide by means 
of sulphuretted hydrogen (see page 165) in 

* Instead of re-dissolving, it can be dried and weighed as me¬ 
tallic copper, giving approximately the percentage of this metal 
in the ore. 






MANUAL OF ASS A YING. 


362 

acid solution, or by solution of sodium thio¬ 
sulphate (hyposulphite of soda), and the sul¬ 
phide re-dissolved and estimated as described. 

Manganese is not often found in copper 
ores in sufficient quantity to interfere. If 
present, it may be removed by adding to the 
ammoniacal solution sodium carbonate, and 
a few c.c. of bromine water, and boiling. 
When cool add the standard solution in the 
usual manner. 

Arsenic does no,t interfere, excepting in the 
presence of iron, when it forms an arseniate 
soluble in ammonia, and gives rise to a brown¬ 
ish color in the liquid. It may be removed 
by adding magnesium sulphate (epsom salt) 
in excess. As soon as a precipitate is no 
longer formed, and the solution has recovered 
its characteristic blue color, run in the stand¬ 
ard solution. 

Silver .—If this be present to any great ex¬ 
tent, it may be removed by adding a few 
drops of hydrochloric acid to the solution, and 
filtering before the addition of ammonia. (Or 




APPENDIX. ^63 

the hydrochloric acid may be added at same 
time as the nitric and sulphuric acids.) 

Iron. —This, in the state of ferric hydrate, 
does not interfere chemically, but obscures 
changes of color by its being disseminated 
throughout the solution ; hence, it must be 
allowed to settle after each addition of the 
standard solution. It may be kept in solu¬ 
tion by means of tartaric or citric acid. 

If it is allowed to be thrown down by the 
ammonia, whether to be removed by filtration 
or not, it should be borne in mind that in 
the case of ores very rich in iron, the iron 
precipitate will retain copper, which cannot 
be dissolved out of it by either boiling water 
or ammoniacal water. Up to about five per 
cent of iron, no special pains need be taken, 
but above that amount, the copper ought to 
be first removed from the solution by sul¬ 
phuretted hydrogen, then dissolved as usual. 

Lead, bismuth, antimony, and magnesia do 
not interfere. 

Lime in large quantity tends to confuse the 







364 


MANUAL OF ASS A YING. 


results ; it may be removed by addition of 
oxalate of ammonia. 

The preceding statements regarding inter¬ 
ferences are well borne out by a series of ex¬ 
periments carried on by Messrs. Torrey and 
Eaton, New York, and described in the En¬ 
gineering and Mining Journal ’ New York, 
May 9, June 9 and 27, 1885. T'he results, 
in brief, were as follows : 

Zinc: 3 per cent caused an (apparent) in¬ 
crease of J per cent copper. 

Arsenic: From 5 to 15 per cent did no harm. 

Silver: 25 per cent caused an error of 

only y 1 ^ per cent copper. 

Iron: 30 per cent caused a loss of 3.71 per 
cent copper. 

Lead: From 5 to 40 per cent had no in¬ 
jurious effect. 

Bismuth: 20 per cent allowed the same 
approximation as the silver. 

Consult the above article, also “ On the 
Volumetric Determination of Copper by 
Means of Potassic Cyanide,” by J. J. and C. 




APPENDIX. 


365 


Beringer, Chemical News , Vol. XLVIII, No. 
1,241, Sept. 7, 1883, pp. 111—113, and Sutton 
and Hart on volumetric analysis. 

IV. AMALGAMATION ASSAY OR LABORATORY 

MILL RUN. 

By M G. Nixon, M.E. 

The wet copper assay bears somewhat the 
relation to the fire copper assay that the fire 
gold assay does to the amalgamation gold 
assay. 

In a certain sense, no one cares to know the 
ultimate amount of metal that an ore contains. 
What is desired in practice, is the yield under 
the most skilful treatment, and this informa¬ 
tion is approximately obtained by fire for 
copper, and the amalgamation process for 
gold. 

There are those so practised in “panning,” 
that from a “panful” of “pulp” they can 
very closely guess the yield by the number of 
“colors” and their size. Of course this 
method is not very popular, nor can it ever be. 



366 


MANUAL OF ASS A YUNG. 


Something more a matter of weighing, and 
less a matter of judgment and practice is 
required. 

The amalgamation assay in its simplest 
form consists in “panning” a weighed amount 
of “ pulp ” with few or many drops of mercury, 
accordingly as the ore is poor or rich. The 
tailings are washed out as clean as may be, 
the pan is then placed over a fire to dry and 
then what remains of dirt and dust is blown 
out with the breath ;• the pan is again placed 
over the fire and the mercury volatilized, leav¬ 
ing the gold (“retort”) ready for weighing. 
This process is quite largely followed by pros¬ 
pectors in some of our free-gold districts. 

An improvement on the method just de¬ 
scribed consists in grinding the pulverized ore 
in a large iron mortar with which water and 
mercury are introduced, with the pestle. 
When the grinding is complete, the whole is 
washed into a pan to be collected and finished 
as before. 

These methods are not recommended, but 



APPENDIX . 


367 


may be resorted to when other apparatus can 
not be obtained. 

The third method consists in grinding say 
ten or twenty pounds of ore in a laboratory 
“arrastre” by hand two hours or more, or, 
where possible, by power half as long. It is 
well to pass the ore through a 40-mesh sieve 
before placing it in the “ arrastre.” From 
two to four ounces of mercury are then 
squeezed through a piece of chamois skin, or 
blown through a tube the end of which is 
drawn out so as to make a pin-hole exit. 
Having put the pulp and mercury into the 
“ arrastre ” mortar, a piece of potassium cya¬ 
nide as large as the end of one’s little finger 
is dropped in, the grinder adjusted, enough 
water added to cover the ore, and the grind¬ 
ing performed. After it is finished, the 
grinder is first washed off into a collecting 
pan, then the mortar with its contents is 
treated in the same manner. The best way 
to collect the amalgam is to hold the pan 
under a running stream or water faucet, and 



368 


MANUAL OF ASSA YING. 


very gently to stir it with the hand. The 
amalgam is then placed in chamois skin and 
squeezed so as to get rid of as much mercury 
as possible. 

The residue is next placed in a small iron 
retort, and what remains of the mercury is 
driven off by heat gradually increased. Of 
course, for reasons of economy, it is well to 
condense the mercury.; it may then be sold to 
mills or others, but neither that portion con¬ 
densed nor that squeezed through the chamois 
should be used over again, since it is almost 
impossible to get rid of the last traces of 
gold. The “retort” is then to be scorified, 
cupelled, inquarted, etc., etc.* 

The writer has saved 93 per cent of the fire 

*An amalgam obtained as a result from either the preceding 
method, from panning with mercury, or from any other process, 
can be treated in the following manner, provided it is not in too 
great quantity. 

Into a new scorifier (say 2^ inches in diameter) introduce the 
amalgam after it has been separated from the free mercury by 
squeezing in a piece of chamois skin. On top of the scorifier 
place another of same size, inverted , having first bored through it 
a hole about l /% inch in diameter. By rubbing down a little the 
tops of the scorifiers, and painting their edges with a thick wash 





APPENDIX. 


369 


assay on the same ore that a mill at the 
time under his superintendence returned 89 
per cent. 

V. PAN TEST FOR GOLD. 

(“ PANNING.”) 

The estimation of gold in ores in which the 
metal is in the free state is unreliable by 

of ground chalk and water, all danger of loss of amalgam by its 
spirting through at the sides, is avoided. 

Heat in muffle or furnace till the mercury has been driven off 
in vapor through the fine opening above, take out, let cool and 
remove the upper scorifier. 

Now put the chamois skin on top of the residue in the scorifier 
and burn to ashes in muffle or furnace, remove a second time and 
cool. 

Finally mix the residue and ashes with granulated lead and 
scorify. Re-scorify with more lead if the resulting button is brit¬ 
tle. Cupel in the usual manner and treat the bead obtained as 
gold bullion. 

If it is not thought worth while to save the mercury, the fluid 
amalgam can be treated directly as described without first squeez¬ 
ing through a chamois skin, in which case the accompanying step 
of burning the latter, etc., is dispensed with. Heat very gradually. 
Even with this apparatus the mercury can be saved by attaching 
to the upper scorifier a small iron tube which bends over and dips 
into water. 

The advantages of the above method are that it is simple, easy 
to operate, and that all the work (up to the cupellation) is done in 
one vessel, and so any liability to loss of gold in transferring from 
a retort, etc., is done away with. Furthermore, working with 
small quantities of amalgam, in even the smallest retort obtainable, 
is unsatisfactory.—W. L. B. 



MANUAL OF ASSAYING. 


either the crucible or scorification process, 
owing to the impossibility of securing an 
average sample. 

The ore, for supposition, may be of such 
value that even when put through a ioo-mesh 
sieve one flake that would go through such 
a mesh could represent the amount of gold 
in two assay tons. 

If then of two assay tons of ore of the above 
character, one is taken, it must run either 
nothing or double the true value of the ore. 

Again, on low grade ores and with the 

charge most convenient to employ, the result 

\ 

or weighable button is so small that its esti¬ 
mation is liable to error. 

Many ores containing small quantities of 
gold are frequently profitable to work, as in 
the case of placers and of large quartz ledges 
where the rock is soft and gold free. In such 
cases the assay report based upon the small 
quantity of ore used in the scorification, or 
even in the crucible assay, is unsatisfactory for 
this and the previous reasons. 



APPENDIX . 


3/i 


Here, then, we resort to the pan test, for by 
it we can treat large amounts of ore, and the 
greater the quantity operated upon the more 
reliable the result. 

The pan test is a process of concentration 
(doing on a small scale that which concentra¬ 
tors effect on the large), the product being 
either gold particles, or gold sulphurets, iron, 
sand, etc., depending on how far the process 
is carried. 

% 

The pan itself is a Russia sheet iron vessel 
of a shallow truncated conical shape (diameter 
about 16|r inches). That form sold by min¬ 
ing outfit establishments has been found 
most useful in practical operations. A round 
shallow wooden dish with its bottom sloping 
to a point, and technically known as a 
“ Batea,” is a useful modification (fig. 116, 
page 138; size of batea: diameter, 17 inches; 
depth, i£ inches; thickness, f inch; angle of 
sides, 12 0 ; material, Honduras mahogany). 
Each person will exercise his own choice after 
learning the operation. After the requisite 



372 


MANUAL OF ASSAYING. 


skill has been acquired, a pan can be extem¬ 
porized from almost any kind of dish, or a 
section of bullock’s horn or an iron spoon 
may serve as substitutes. 

The requisite amount of ore from ioo to 
500 assay tons (5 to 25 pounds, or in French 
weights 3 to 15 kilos), depending upon its 
richness, is sampled, crushed and pulverized 
as directed in the chapter on gold and silver 
ore. The pulverization, however, need be 
carried no finer than to cause the ore to pass 
through a 40, 50 or 60 mesh sieve (the latter 
preferred). Weigh now the ore and put in 
the pan, which latter must be free from 
grease. Moisten and let it stand for a few 
moments in order that particles may not float 
off when the pan is put in water. 

When wet, the whole pan and ore is gently 
sunk below the surface of a tank of water (a 
common wash tub will do nicely in the labora¬ 
tory). A peculiar oscillatory motion or side 
vibration is commenced, though not enough 
to throw any particles of ore over the edges 



APPENDIX. 


373 


of the pan. The object of this is to settle the 
heavier particles (the free gold, heavy miner¬ 
als, black sand, etc.), and have nothing on the 
surface but rock or quartz ; a little experience 
will teach the point. Then slightly incline 
the pan, and so wash it around as to carry the 
surface rock over the edge ; only a little at a 
time, however. 

Level the pan and resettle as at first ; again 
incline and wash more over the edge. Keep 
up this operation, gradually getting more and 
more rock over the edge, and becoming more 
careful and washing more delicately as the 
process continues. 

Toward the end of the operation, that is, 
when the rock is nearly gone, be careful to 
keep the ore under the surface of the water, 
as the gold might otherwise become dry and 
float off. Also make no sudden or unusual 
lurch, or the whole result may go off the pan. 
The above manipulation is far more difficult 
to describe than to perform after having once 
been acquired. Dry the residue. 



374 


MANUAL OF ASSA YING. 


If gold alone is obtained, that is, gold (or 
gold and silver) free from sulphurets, etc., it 
must be treated as an alloy, weighed, parted 
and weighed again, or cupelled with lead, 
weighed, parted and weighed ; in both cases 
giving gold and silver. 

If the panning is not carried to such a point 
as to get rid of all the rock, the concentration 
is all scorified with test lead (or run down in 
a crucible), cupelled, parted and weighed. 
In the case of an ore supposed to carry aurif¬ 
erous sulphurets it should be panned so far 
as can safely be done without losing metallif¬ 
erous particles and the concentration treated 
as above described. 

If the ore is quite poor, or a large quantity 
is desired to be worked, the panning can be 
carried on roughly and the successive con¬ 
centrations finally panned together. 

The results are based upon the amount of 
ore taken in the pan. If much of this work 
was to be done, a set of weights from 500 
A. T. down (approximately accurate) would 



APPENDIX. 


375 


be very convenient and save calculation. The 
result would be as many times the number of 
ounces contained in the ore as the quantity 
of ore was more than one assay ton. 

For example, the ore was supposed to be 
very poor and therefore : 

500 A. T. were taken. 

Bead weighed 50 mgrms. 

500 A. T. : 1 A. T. :: 50 mgrms. : y 1 ^ mgrm., 
or the ore ran y 1 ^ oz. Troy per ton. 

If 100 A. T. had been taken and the same 


weight bead obtained, we would have : 

100 A. T. : 1 A. T. :: 50 mgrms. : % mgrm., . 
or the ore would run ^ oz. Troy per ton. 

As an example of the calculation required 
without the large assay ton weights, I give 
the following : 

Weight of panful of ore, 2^ kilogrammes^2,250,000 
milligrammes. 

Weight of bead obtained, gold 20 mgrs., silver 50 mgrs., 


then 


2,250,000 mgrms. 29166 


20 mgrms. 


x 


X 


2 5 


_LiL_ 07 

100 


and 2 ,250.000 mgrms. ,, 29166 x ^ oz , 
50 mgrms. X 1 u 


The free gold can be separated from the 







3 7 6 


MA NUA L OF A SSA YING. 


sulphurets (if it be desired to determine how 
much of the gold is “free” and how much in 
the “sulphurets”) by washing in an amal¬ 
gamated pan. Such a vessel may be simply 
made by bending a piece of thin silver-plated 
copper (about 6 inches by 12 inches) so as to 
form curved edges on three sides, the silvered 
sides in. The side not turned up is one of 
the narrow ends. A little mercury (free from 
gold and silver) will quickly amalgamate the 
interior, and if the ore is washed carefully 
over this, most of the free <^old will become 
amalgamated and stick to the pan. A piece 
of chamois skin made into a rubber will push 
the gold, which can be seen as little specks of 
amalgam, to the open edge of the pan and 
into a crucible. The mercury can be driven 
from the gold by heat. 

No investigation has been made to deter¬ 
mine if any silver is carried by the mercury 
to the assay from the pan, but if such be the 
fact, the result is still accurate for gold. If 
carefully performed the results ought to be 



APPENDIX. 


377 


above the yield from a stamp-mill with amal¬ 
gamated plates. 

A more common test than with the above 
silver-plated amalgamated copper pan, is, after 
having panned down, to drop a few globules 
of clean “quicksilver” (i.e., mercury) into 
the pan and a little cyanide of potassium (to 
keep the mercury clean). Work up with a 
spatula till the mercury has taken up the free 
gold, then collect, and run off the mercury. 
Clean it and dissolve in nitric acid (for the 
gold only) or drive off the mercury in the 
muffle, weigh the residue of gold and silver, 
part and weigh gold. 

The residue in the pan should then be 
assayed and the gold and silver (actual 

weight) determined. Suppose 

Original weight of ore.2^ kilos. 

Gold and silver after retorting.35 mgrms. 

Gold after parting.15 

Hence silver.20 mgrms. 


Gold in sulphurets 
Silver “ 


50 mgrms. 









MANUAL OF ASSA YINC. 


3TB 

Then we have : 

Free gold y 1 ^ oz. per ton of original ore. 

Silver in free gold ^ 5 0 - oz. per ton of original 
ore. 

Gold in sulphurets y 6 ^ oz. per ton of original 
ore. 

Silver in sulphurets i t V 6 o oz - P er ton of origi¬ 
nal ore. 

Total gold y 8 ^ oz. per ton of original ore. 

Total silver iyLL- oz. per ton of original ore. 

There is a certain loss in panning, hence 
the results are not analytically accurate, but 
are close indications of the practical result of 
the working of gold ores in a mill with copper 
plates.* 

VI. CHLORINATION ASSAY OF GOLD ORES. 

If gold exists free in the gangue, that is, 
not combined with sulphur, arsenic or tellu¬ 
rium, it can be chlorinated directly without 
roasting. 


* For the information comprised in the above article I am 
largely indebted to Mr. S. A. Reed of Irwin, Col., and Mr. Ray 
G. Coates of Chicago, 



APPENDIX. 


379 


But sulphurets, arseniurets or tellurides 
must be first roasted and ■ thoroughly at that. 

The chlorination can be done in the labora¬ 
tory on either a large or moderately large 
scale. Bor the former, operating say on 20 
pounds (y-g-Q of a ton),.consult the section in 
Kustel, entitled “ Extraction of Gold from 
Sulphurets, Arseniurets or Quartz, by Chlor¬ 
ination,” pp. 136-139. 

For the latter grind up 5 to 8 ounces (or 5 
to 10 A. T.), and, if necessary, roast in the 
usual manner. Use a frying pan for this 
purpose, and see that the sulphur is entirely 
driven out so that no smell (as of a burning 
match) is perceptible at the finish. Cool, 
grind in an iron mortar, and re-roast at a red 
heat. 

When cold, reserve 1 A. T. of the ore for 
regular assay; the remainder is to be chlori¬ 
nated in the apparatus herewith described. It 
consists of a flask, provided with a funnel tube 
for acid supply and delivery tube for the chlor¬ 
ine gas generated. The latter tube dips into 





MANUAL OF ASSA YING. 


380 

a wash bottle containing water to wash the 
gas. From the latter the gas passes up into a 
separatory funnel containing the ore. The 
exit tube from the funnel may pass into a flue 
or the open air, or into a cylinder holding 
shavings moistened with alcohol. 

Place in the flask a mixture of 3 parts of 
black oxide of manganese, 4 parts of common 
salt, and 4^ parts of water, all well mixed. 

Place the ore, which has been dampened 
with water, in the separatory funnel, having 
put in at the bottom a very little cotton to 
prevent the tine ore from stopping the pas¬ 
sage of the gas. 

Having now made all ready, pour down 
through the funnel tube parts of sulphuric 
acid at intervals. After a time the flask is to 
be gently heated, that all the chlorine may be 
driven off. 

Run the operation for about two hours, 
then disconnect the flask and let the funnel 
stand over night. Finally take out the upper 



APPENDIX. 


38^ 

cork and wash out the chloride of gold with 
distilled water. 

To the solution in a beaker or tumbler add 
a few drops of hydrochloric (muriatic) acid, 
then some solution in water of sulphate of 
iron (green vitriol or copperas), stir with a 
glass rod, warm and let stand undisturbed 
until all the gold has been thrown down to 
the bottom and the liquid above is perfectly 
clear. Half of this liquid is drawn off with a 
syphon, the remainder containing the gold is 
filtered as usual, washing with warm water. 
Dry the filter, burn, scorify ashes and cupel, 
or cupel directly with sheet lead, weigh, etc. 
Compare result with unchlorinated sample. 
Consult Kustel as above, and Aaron’s “ Leach¬ 
ing Gold and Silver Ores,” p. 90, on the “Work¬ 
ing Test.” 

VII. CHLORINATION TEST FOR SILVER. 

In smelting-works it is often necessary to 
test ores that have been subjected to chlorid- 
izing roasting, to ascertain the amounts of 
chloride of silver contained in them. Two 
assays are made of each ore. 



MANUAL OF ASSAYING. 


382 

Several pounds of the ore are taken from 
various portions of the entire lot, well mixed 
and sifted. From this, weigh out two charges 
of y 1 -^ A. T. Scorify and cupel one charge in 
the usual manner. 

The other charge is brushed into a filter 
paper held in a glass funnel, and over it pour 
a warm solution of hyposulphite of soda (six 
or eight ounces in a quart of water), which 
rapidly dissolves the chloride of silver from 
the ore. Continue this treatment until a 
small portion of the filtered liquid contained 
in a test-tube, darkens but slightly and does 
not lose its transparency upon the addition of 
a few drops of a solution in water of sulphide 
of sodium. 

Wash the mass in the filter with warm 
water, remove filter and all, dry and burn in 
scorifier in muffle, at a low heat, mix pshes 
with lead, scorify and cupel as usual. 

(The hyposulphite solution dissolves out 
sulphate of silver as well as the chloride. If, 
as is sometimes the case, it is desired to know 




APPENDIX. 


the amount of sulphate present, leach a third 
charge with warm water, which will take out 
the sulphate, but will not touch the chloride 
or any unacted-upon ore. Scorify and cupel 
the residue as directed.) 

The difference between the two cupellations 
shows the amount of silver which has been 
changed into the state of a chloride. Thus : 

i st charge ran 180 oz. per ton. 

2d charge ran io oz. per ton. 

Hence, 180—10=170 oz. of chloridized pulp. 

To obtain percentage : 

180 : 170:: 100 : x — 94.4 per cent. 

“ If there should be gold in the ore, this 
must be subtracted from both assays, because, 
although the amount of gold would be equal, 
the chlorination result, as it should be, must 
come out higher after the gold is subtracted.” 
(Kustel.) 

VIII.— THE ASSAY OF GOLD AND SILVER BULLION. 

The larger portion of this article is taken 
from the Fourth Annual Report of the State 



3§4 


MANUAL OF ASSAYING. 


Mineralogist of California for the year ending 
May 15, 1884, by the kind permission of Mr. 
Henry G. Hanks, State Mineralogist. His 
very able and complete paper could hardly be 
improved, hence the extracts are given almost 
vej'batim , as many will not succeed in obtain¬ 
ing copies of the report, the edition of which 
is already exhausted. 

The remainder of the description is made 
up partially from information given me per¬ 
sonally by Mr. F. E. Fielding, assayer of the 
Consolidated Virginia and Consolidated Cal¬ 
ifornia Mines, of the Comstock Lode, Virginia 
City, Nevada, and partially from other sources, 
together with a little as the results of personal 
experience. 

Bullion, or the precious metals in bars more 
or less impure, is of very varying composition, 
running down from that which is mostly gold, 
through mixtures where the gold and silver 
are more equally divided, and where the silver 
predominates (all containing various impuri¬ 
ties or base metals, as lead, copper, etc.), to 



APPENDIX. 


385 


base bullion, or that in which the lead is in 
excess of all the others. The latter kind is 
treated of in another portion of the appendix. 
Here I consider only those bullions in which 
the gold and silver form the greater amount. 

Absolutely accurate assays of gold and sil¬ 
ver bullion require care, skill, and first-class 
apparatus. The skill may soon be acquired 
by practice, but the apparatus must not only 
be of the very best quality, but must be kept 
in the most perfect state of adjustment. It 
is not enough to purchase chemicals which 
are marked “p ure >” or a balance supposed to 
be accurate. The chemicals must be tested, 
and the accuracy and adjustment of the bal¬ 
ance and weights verified, before correct re¬ 
sults can be certain. 

The process of assaying gold and silver 
bullion is divided into several operations, as 
follows : Melting and refining the crude bull¬ 
ion, and casting the bar, cutting the assay 
chips, or otherwise preparing the assay sam¬ 
ples, the preliminary assay, the assay proper, 




3 86 


MANUAL OF ASS A YING. 


calculating the results, weighing the bar, and 
stamping the fineness and value upon it. 

Melting ; refining, einel casting the crude bull¬ 
ion .— For melting, a wind furnace is best, but 
a good coal stove, such as used in offices, will 
answer the purpose if the amount operated 
upon is small. 

The wind furnace is a square box of fire¬ 
bricks, built in the form of a cube of three- 
foot face, with an opening in the centre of the 
upper face. The fire-box is about a foot 
square, and fourteen inches deep, provided 
with an ash pit, movable grate, bars, and slid¬ 
ing cast-iron cover. The flue should be a 
horizontal opening, about three by six inches, 
near the top of the fire-box, and connected 
with a chimney at least thirty feet high, to 
insure a good draft. The furnace can be 
built by any bricklayer of ordinary skill and 
judgment. No mortar should be used in lay¬ 
ing the fire-brick, but good clay, mixed with 
a portion of coarse sand, substituted. 

The bullion is generally melted in a black 








APPENDIX. 


387 


lead crucible. Before such a crucible can be 
safely used, it must be annealed. Were this 
neglected, and it should be placed in the fire 
without this precaution, it would soon fly to 
pieces. This is caused by the water it con¬ 
tains being converted into steam ; and the 
structure of the material being such that the 
steam cannot make its escape, destruction of 
the crucible follows. It is best to commence 
annealing the crucible some time before it is 
wanted. It should be set near the hot fur¬ 
nace for several days, and turned occasionally. 
When the fire is nearly spent, it may be 
placed, rim downward, upon the hot sand, 
generally placed on top of the furnace. A 
day or two of such treatment will make it 
safe to hold it over the open furnace by the 
aid of the crucible tongs or poker. After it 
has been frequently turned, and is hotter than 
boiling water, it is safe to place it, rim down¬ 
ward, upon the burning coals. After the rim 
is red hot, all danger is passed, and it may be 



MANUAL OF ASSA YING. 


388 

turned, and placed in position for the recep¬ 
tion of the gold. 

If the fuel is charcoal, it will be best not to 
use small pieces, or, at least, not coal dust. 
Pieces the size of an egg, or larger, will make 
the best fire. When the crucible becomes 
red hot, a long piece of quarter-inch gas pipe 
is used to blow out any dust or ashes that 
may have fallen into it. A cover is then 
placed on the crucible, and lumps of coal built 
up around it with a long pair of cupel tongs. 
When the crucible has attained a full, red 
heat, one or two spoonfuls of borax, wrapped 
in paper, are placed in it, using the cupel 
tongs. When the borax has melted, a small 
quantity of the bullion, also wrapped in paper, 
is placed in the crucible in the same manner. 
Several portions may be thus added, accord¬ 
ing to the size of the crucible. A fresh sup¬ 
ply of charcoal must be built up around the 
crucible when required, the cover having been 
previously replaced. When the bullion has 
melted down, more is added in the same man- 





APPENDIX. 


389 


ner, until the crucible has received all that is 
to constitute the bar. In the meantime, the 
ingot mould, in which it is intended to cast 
the gold, must be made smooth and clean 
inside. This is best done by rubbing with 
sandpaper and oil, or with a dry piece of 
pumice stone. It is then wiped d*ry and clean 
with a rag, oiled slightly, and placed on the 
edge of the furnace in such a position that 
it may become quite hot; not so hot, how¬ 
ever, as to approach redness, nor to cause the 
oil to burn. 

When the bullion is in a fluid state in the 
crucible, the mould must be placed on a level 
surface, and oil poured into it. To make a 
clean bar, it will be found best to use consid¬ 
erable oil — sufficient to cover the bottom of 
the mould to the depth of at least one-fourth 
of an inch. The mould should be turned in 
such a manner as to allow the oil to flow to 
all parts of its interior, and then placed again 
level, and in the position it is to occupy while 
casting the bullion. If the latter is clean, 



390 


MANUAL OF ASSAYING. 


and the quantity less than fifty ounces, it is 
best not to attempt to skim it. Two spoon¬ 
fuls of nitrate of potash may be added, and 
one of carbonate of soda, and the whole 
allowed to melt and flow over the surface of 
the melted metal. When very hot, and the 
slag perfectly fluid, the crucible is lifted from 
the furnace, and with a bold and steady hand, 
its contents are poured into the mould, the 
crucible being held for a little time in an 
inverted position, to allow the last portion of 
metal to flow from it. The oil inflames, and 
remains burning on the slag, which flows 
evenly on the surface of the bullion. If the 
mould is clean, and of the right temperature, 
and if sufficient oil is used, a clean bar will 
result. A little practice will enable the ope¬ 
rator to hit the exact conditions. The oil 
used should be a cheap animal oil ; common 
whale oil answers every purpose ; lard oil is 
also well suited ; coal oil is too inflammable, 
as well as dangerous, and should never be 
used. When cold, the bar falls easily from 



APPENDIX. 


391 


the mould. A slight tap with a hammer sepa¬ 
rates the slag, and the bar may be cleaned 
with water and nitric acid, or, if necessary, 
with sand and a suitable brush. A good plan 
is to place the bar in the furnace until it 
becomes nearly red hot, and then to quench 
it suddenly in water. This will ,,be unneces¬ 
sary if proper precautions have been observed 
in preparing the mould. 

When the bullion is very impure — which 
is the case when in the form of retorted amal¬ 
gam which has not been properly cleaned — 
a different method of treatment should 'be 
adopted. A large-sized crucible will be re¬ 
quired. Three or four times the amount of 
flux must be put in, with the addition of a 
spoonful of carbonate of potash. A skimmer 
must be prepared by forming the end of a 
large wire, about the size of a common lead 
pencil, into a spiral about an inch and a half 
in diameter, and bending it so that when the 
skimmer is let down vertically into the cruci¬ 
ble the spiral will lie flat upon the surface of 





392 


MANUAL OF ASSAYING. 


its contents. A bucket of water is set near 
the furnace, and when the slag has become 
fluid, and it is beyond question that the bull¬ 
ion has become perfectly melted, the skimmer 
is touched to the slag and gently moved from 
side to side ; a portion of the slag adheres to 
the iron, the skimmer is removed and plunged 
into the water, and immediately replaced in 
the crucible ; an additional portion attaches 
itself to the skimmer, which is again quenched 
in water. This is repeated until a large por¬ 
tion of the slag is removed, and a new charge 
of flux, consisting, this time, of borax and 
nitrate of potash, is allowed to fuse upon the 
surface of the bullion. The first flux is re¬ 
moved from the skimmer by a slight blow 
with a hammer, and the crucible is skimmed 
with it as before. This must be repeated 
until all iron and other impurities have been 
removed, and the surface of the molten metal 
appears, when exposed, clean and reflective 
as a mirror. It may then be poured into the 
mould, as described before. Care should be 




APPENDIX. 


393 


taken not to dip the wet skimmer beneath the 
surface of the bullion, or an explosion will 
take place. 

In large meltings it is customary always to 
skim the bullion before pouring, and so far to 
remove the slag that any remaining portion 
may be left on the sides of the cfucible, and 
the metal only allowed to How into the mould. 
This requires some skill and considerable 
practice. As it is imperative that the bar 
should be homogeneous to insure a correct 
assay, it is usual to mix the melted metals 
thoroughly before pouring. This is done in 
the large way by stirring just before lifting 
from the furnace. It may be done with an 
iron rod, with a piece of black lead held with 
the tongs, or with a clay stirrer made specially 
for that purpose, in which case it will be nec¬ 
essary to allow it to remain in the crucible 
until it has acquired the temperature of the 
fused metal ; otherwise, a portion of the bull¬ 
ion may attach itself to the stirrer, and be re¬ 
moved with it. In small meltings it will be 



394 


MANUAL OF ASSA YING. 


found sufficient to mix the bullion by giving 
the crucible a rotary motion while holding it 
with the tongs just previous to pouring. This 
must be done so quickly that the crucible has 
no time to cool. For very small fusions it is 
best to use a small Hessian crucible, and, 
when the bullion is melted with plenty of flux, 
to set it aside to cool, and then break the cru¬ 
cible, and separate the pieces of crucible and 
portions of slag by slight blows of a hammer 
on the edges of the button. It is very diffi¬ 
cult to pour small quantities of gold without 
loss from portions remaining on the sides of 
the crucible. 

Preparation of samples for assay .— When 
the bar is clean, a small portion must be 
taken from different parts for assay. This 
is done in several ways, very frequently by 
cutting pieces from opposite corners or edges 
with a cold-chisel or hollow punch, but this is 
extremely clumsy, and in every way inconven¬ 
ient. If the bar is brittle, a much larger 
piece may break off with the chip than is re- 




APPENDIX. 


* 


395 


quired. If the proper-sized chip is cut off 
successfully, it is likely to fly away and be 
lost. A second way of sampling is to bore 
into the bar, top and bottom, with a small 
drill. This may be done in a lathe or by 
means of a ratchet drill. The bar should 
be placed in a clean, copper pan,* so that nQ 
loss may occur ; the surface borings, resulting 
from the first revolutions of the drill, should 
be rejected. Those that follow, to the extent 
of a little more than one gramme, are to be 
placed in a suitable vessel, and carefully pre¬ 
served for assay, each lot separate. Before 
cutting or boring the bar the number of the 
assay should be stamped upon it, and the 
same number placed with the clippings or 
borings. This number should represent the 
bar through every stage of the assay by which 
its value is ascertained. Some assayers stamp 
the initial of their name on the cut faces, so 
that no portion can be removed after it leaves 
their hands. A third manner of sampling is 
that by “granulation.” While the bullion is 



396 


MANUAL OF ASSA YlNG. 


still in the melted state in the crucible, but is 
already refined, it is well stirred, and two 
samples are scooped up with a small ladle, 
one from the bottom of the crucible, and the 
other from the top. Each ladleful is poured, 
slowly and carefully, and in a narrow stream, 
into a clean copper basin containing warm 
water, which is rotated quietly by means of a 
broom or paddle. Keep the resulting granu¬ 
lated metal from top and bottom of the cruci¬ 
ble apart, drying each lot. 

The selected pieces of the granulations, or 
the chips cut from the bars, are flattened on 
the anvil and passed through the rolls until 
thin enough to be readily cut by the snip- 
shears. (Fig. 102.) They, or the borings, if 
borings are taken, are now ready for weigh- 
ing. 

Weights and weighing .—For the bullion 
assay a special set of Weights known as 
“gold weights” is used. As the basis of 
the bullion assay is 1,000 parts, so the 
unit of the “gold weight” system is a 1,000 



APPENDIX. 


397 


piece, from which the weights range down 
to a T ofoo pi ece * The actual weight of 
each piece in this system is one-half of 
its corresponding piece in the French or 
metric system; thus the 1,000 piece weighs 
actually 500 milligrammes, and so on. Gold 
and silver in bullion are always reported in 
thousandths; that is, in parts of one thousand, 
taken, as before stated, as the standard of the 
assay; hence the use of the weights described. 
By difference between the fineness and the 
i,ooo, we learn the number of parts of the 
base metal contained in the bullion. Thus, if . 
1,000 parts of a bullion, after treatment, 
weighs 900 parts, it has a “fineness” of 900, 
or it is 900 “fine,” and the base metal is 100. 
In weighing, always remember that the rider, 
or index needle, when marking tenths for 
gold, is to be multiplied by two, as each mark 
on the beam or index plate only represents 
y 1 ^- in the metric system, while it should be T 2 y 
for the “gold weight” system. Half-tenths 




MANUAL OF ASSAYING. 


398 

are always reported in the tables for gold, but 
not in those for silver. 

As shown from the preceding, the metric 
weights can be employed if the “gold 
weights” are not obtainable. 

The method of weighing is conducted as 
follows: The assayer seats himself before the 
balance, having the clippings or borings in a 
convenient position inside the case. A 1,000 
piece (or half a gramme weight) is placed in 
the right-hand pan of the balance, and por¬ 
tions of the clippings or borings in the other 
• until nearly correct, but the bullion should be 
in excess. The largest piece is then removed 
by the aid of a pair of pincers, and a small 
corner cut off with the shears. This done 
once or twice will nearly balance the pans; 
but by touching the piece, of bullion selected 
against a clean file, still more minute portions 
can be removed. By careful manipulation 
nearly the exact point will soon be obtained; 
but with the greatest care, if the balance is 
delicate, it will be found nearly impossible to 




APPENDIX. 


399 


adjust the weight so perfectly that the index 
needle will not point either one side or the 
other of the zero. In such a case, it will be 
necessary to make a memorandum of the 
error, and mark it with the number of the 
assay, and in weighing the cornet, to take the 
same reading of the index needle. 

Preliminary Assay .—It has been found that 
silver cannot be dissolved out of an alloy of 
that metal with gold, unless the proportion of 
silver is at least two and one-half times that 
of the gold. If a larger proportion is pres¬ 
ent, the gold is left after the extraction of 
the silver in the form of a powder, and can¬ 
not be dried and weighed without danger of 
mechanical loss. If less, the gold protects 
the silver, and the action of the acid ceases, 
while some of the silver remains undissolved. 
An alloy of three parts of silver to one of 
gold was formerly taken, from which the 
terms quartation and inquartation come; but 
of late years the above proportions have been 
found to be best. 




400 


MANUAL OF ASSAYING. 


In order, then, to form such an alloy, the 
assayer should know the amount of silver in 
the bullion, that he may consider it in adding 
silver to a bullion mostly gold, or gold to a 
bullion nearly all silver. The following imag¬ 
inary and reversed bullions will illustrate 
this point plainly: 

BULLION NO. I. 

200 parts gold need 80 parts more to make 280 parts. 

700 “ silver = times the 280 parts gold. 

too “ base metal. 

1,000 *' 

BULLION NO. 2. 

700 parts gold 

200 “ silver need 1,550 parts more to make 1,750 parts = 

2 \ times the 700 parts gold. 

100 “ base metal. 

1,000 ‘ ‘ 

The proportions of silver and gold in the 
bullion in question are ascertained in several 
ways. First, by merely looking at the bullion, 
having had previously such experience with 
similar alloys that the knowledge becomes 
almost instinctive. Secondly, by direct com¬ 
parison with slips of known ‘‘fineness.” Third¬ 
ly, by use of the touchstone and needles. 





APPENDIX . 


401 


(For the methods of making and using the 
latter, see the article in Mr. Hanks’ Report.) 
Fourthly, by a preliminary fire assay. This 
is by far the best way, and should always be 
done where great accuracy is required. 

Take the 1,000 parts of the bullion already 
weighed out, wrap in a piece of pure sheet 
lead of about 2 grammes (30 grains or so) in 
weight, cupel and weigh the resulting bead. 
If it seems mostly silver, roll it out, boil in 
nitric acid of 32 0 Beaume (1.26 sp. gr.), 
decant, wash, dry, ignite, and weigh the gold. 
If the bead appears very yellow, add three or 
four times as much pure silver, wrap up to¬ 
gether in sheet lead, recupel, part as above, 
and weigh the gold. The latter may come 
down as a fine powder, and a slight loss occur 
in washing, but the results will be sufficiently 
accurate for the purpose. 

From the data obtained above, it will be 
easy to make up the proper alloy for the 
regular assay and the proof centre, as shown 
by the following simple examples: 




402 


MANUAL OF ASSAYING. 


Example No. /. 

Suppose the 1,000 parts of bullion taken 
weigh, after cupellation, 520.5 parts, then 
479.5 parts (1,000 — 520.5) are base metal. 

The gold, after parting, weighs 15 parts. 

These figures enable us to prepare the 
assay proper and the proof centre, as hereby 
shown: 


Gold and silver bullion taken.1,000.0 parts. 

“ “ “ after cupellation. 520.5 “ 

Leaving base metal. 479-5 “ 

Gold and silver after cupellation. 5 2 °-5 parts. 

“ after parting. 15.0 “ 

Silver in the bullion. 5°5-5 “ 

505.5 X 2.5 = 202.2 parts. 

Deduct gold already in the bullion. 15.0 “ 


U 


Leaving gold to add. 187.2 

Hence: 

Bullion f composed of Proof centre. 

505.5 parts silver = 505.5 parts silver 

479.5 “ base 

15.0 “ gold ) 

gold to add ) 


take 

1,000.0 parts 




187.2 

1,187.2 


<< 


il 


total. 


= 479-5 

“ copper. 

= 202.2 

“ gold. 

00 

“ total 



















APPENDIX. 


403 


Example No. 2. 


Gold and silver bullion taken . ... 


“ “ “ after cupellation.. 

. 764-4 “ 

Leaving base metal. 

. 2 35-6 “ 

Gold and silver after cupellation.. 


“ after parting. 


Silver in the bullion. 


602.1 X 

2-5 = U5°5- 2 parts. 

Deduct silver already in the bullion .... 162.3 

Leaving silver to add. 

.i, 34 2 -9 

Hence: 


Bullion f composed of 

Proof centre. 

take 602.1 parts gold = 

1,000.0 pts. | 235.6 “ base = 

602.1 parts gold. 
235.6 “ copper. 

l 162.3 “ silver ^ 


1,342.9 “ silver to add ) = 

1,505.2 “ silver. 

2,342.9 “ total. 

2,342.9 “ total. 


The silver, gold, and copper added are, of 
course, pure. 

The Assay Proper .— Two assays of a large 
bar are always made, the samples being 
taken from the top and bottom. A proof 
















404 


MANUAL OF ASSAYING . 


centre or '‘check” is always run through with 
each set of assays, and consists of pure gold, 
pure silver, and pure copper in such propor¬ 
tions as shall correspond as nearly as possi¬ 
ble to those of the bullion under trial, as 
shown in the above examples. 

The proof cupel is always placed in the 
centre of the muffle, those for the bullions at 
each side, the object being to correct the loss 
by volatilization. 

The loss in weight of the proof centre bead 
is to be added to each weight of the bullion 
bead. 

Make the weighings of the duplicate bul¬ 
lions, and the gold or silver that is to go 
with each, and also the three metals or so for 
the proof centre. Wrap each lot in a piece of 
pure sheet lead, and squeeze all into a bullet. 

According to the difference in fineness of 
the bullions are the amounts of pure sheet 
lead varied, and the latter must contain no 
gold whatever. Its purity being established, 
it is easily prepared by rolling out to a uniform 




APPENDIX. 


405 


thickness (about inch or so), and about if 
inches wide. The weight of so many inches 
of the lead is determined, and the rest of the 
samples are cut from measurement of the one 
weighed. These pieces are known as “lead 
cornucopias,” and should always be prepared 
by the assayer himself, and kept on hand in 
sufficient quantity. 

If too much lead is used in the cupellation 
of the buttons, the loss in precious metals is 
increased by the greater length of time re¬ 
quired for the cupellation. On the other 
hand, if there is a deficiency in lead, the beads 
are ill-shaped, and are liable to contain some 
of the base metals. If a large amount of cop¬ 
per is in the bullion, the lead must be in¬ 
creased. “ Long experience has proved that 
silver opposes the oxidation of copper by its 
affinity, so that it is necessary to add a larger 
amount of lead in proportion to the quantity 
of silver present.” (Mitchell.) 

In cupelling bullion say from 980 to 1,000 
fine, 30 grains (about 2 grammes) of lead are 




406 


MANUAL OF ASSAYING. 


best used, and for very base bullion, and 
where the base is mostly copper, ioo to 130 
grains (6.5 to 8.5 grammes, nearly) are gener¬ 
ally used. Mark appropriately with ruddle 
three good cupels, place them in the muffle, 
the proof cupel between the other two, as 
directed before, and when hot, a piece of pure 
lead, weighing 3 grammes (about 45 grains), 
is placed in each. The leads will soon melt 
and begin to “drive”; that is, begin to be 
absorbed by the cupel; the assays are then to 
be added, using the cupel tongs. When 
perfectly melted, the cupels are drawn forward 
to that point in the muffle which experience 
has shown to the assayer that cupellation 
progresses most successfully. When the 
cupellation is finished, and the buttons have 
assumed a brilliant metallic lustre, they are 
removed, hammered slightly on their edges 
on a clean anvil, the last blow being given 
near one edge, to make that part thinner, in 
order to facilitate the rolling process which 
follows, and examined with a magnifying glass 








APPENDIX. 


407 


to see that all bone ash has been removed. 
Weigh and note results. The two bullion 
beads should weigh exactly alike; if this 
should not be the case, the heavier one must 
be examined carefully, to see if any particle 
of bone ash may have been overlooked. If 
this should fail, there is no recourse but to 
make another assay, which should agree with 
one of the first. Generally, if care is used, 
the first pair will agree. Then add to the 
weight of the assay beads proper the loss sus¬ 
tained by the bead of the proof centre. Next 
the beads should be annealed; which can be 
done in the muffle, if still hot, or upon char¬ 
coal, with the flame of a spirit lamp urged 
with a blowpipe. After cooling, they are 
passed through the rolls, being drawn into 
ribbons about 2\ inches in length. The proper 
letter or number is stamped on the end of 
each slip, somewhat deeply, and all are then 
re-annealed. Each slip is then rolled up into 
a spiral form upon a glass rod or lead pencil, 
commencing at that end of the slip which is 




408 


MANUAL OF ASSA YING. 


not stamped. A slight pinch, or reverse bend, 
after the rod is removed, will prevent their 
unrolling. The “cornets,” so prepared, are 
then ready for treatment with acid, after 
which step the letters or numbers stamped 
upon them will be as distinctly seen as they 
were before. 

Introduce each cornet into a separate part¬ 
ing flask or matrass, and add i fluid ounce 
(29^ c.c.) of pure nitric acid of 21 0 Beaume 
(sp. gr. 1.16), place on the sand bath which 
acts as cover of the furnace, or on a small 
sand bath supported on the ring of a retort 
stand over a spirit lamp or gas burner, and 
boil until no more red fumes are evolved (say 
ten minutes). Just at the point of coming to 
a boil add one or two “pepper carbons” 
(made by heating whole or unground pepper 
beans to carbonization on an iron shovel or 
pan). They prevent spirting or bumping. 

A folded piece of paper, or a pair of wood¬ 
en tongs, is used to lift the flasks, and the 
acid decanted carefully into some convenient 




A P PENDIX. 


409 


vessel kept to receive it, as the silver is valu¬ 
able, and may be recovered when a sufficient 
quantity has accumulated. The same quan¬ 
tity of 32 0 Beau me acid (1.26 sp. gr.) is then 
poured into each flask, and, being placed on 
the sand bath, again boiled for ten minutes, 
with the “p e PP er carbons” as usual. After 
this, the acid is poured off, and each flask is 
filled up with distilled water, gently rotated, 
and the water decanted and thrown away. 
Repeat the washing, and finally fill, for the 
third time, the flasks with distilled water, this 
time quite to the brim. Over the mouth of 
each flask an annealing cup is placed, mouth 
downward, like a cap, and the flask and cup 
inverted together. By these means the cornet 
is deposited gently, and without loss or injury 
in the cup. The flask is then gently raised 
until on a level with the edge of the cup, when 
with a quick side motion the flask is removed, 
the water from it, of course, running to waste. 
The water in the cup is poured out carefully, 
and the cup and its cornet are heated, at first 




MANUAL OF ASSA YING. 


410 

gently on the sand bath till all the moisture 
has been driven off, then in the muffle to red¬ 
ness, making the third time of annealing. 
Take out and let cool. The gold has recov¬ 
ered its natural color, and is firm enough to 
be handled with pincers. It must next be 
weighed accurately, using the “gold weights” 
(or the gramme weights and multiplying by 
two), and noting any memorandum regarding 
the position of the index in weighing out the 
bullion in the first operation. The weight of 
the cornet in parts of the 1,000 piece (or in 
half milligrammes) will represent the fineness 
of gold in the bar, expressed, as before, in 
thousandths. 

A small amount of silver will always remain 
in the cornet, no matter how carefully the 
manipulations may have been conducted. 
This surcharge , so called, must be deducted 
from the weight of the gold by subtracting 
from it one-half, one, or two thousandths (or 
“points”) accordingly as the fineness ranges 
from 500 to 900, or as experience indicates. 





APPENDIX. 


41 I 

Weighing the Bar .—The next step is to 
ascertain the weight of the bar in troy ounces 
and decimals. This must be done with the 
greatest accuracy. A good bullion balance is 
much to be desired; but a bar can be weighed 
on a defective balance if it is sufficiently deli¬ 
cate to turn distinctly with the hundredth 
part of a troy ounce. This method of weigh¬ 
ing is called counterpoising, and is conducted 
as follows: 

The beam must first be brought to a level 
by putting sand, small shot, or other conven¬ 
ient weights into the lighter pan. When in 
perfect equilibrium, a small weight is placed 
in one of the pans to test the delicacy of the 
movement, and if satisfactory, the bar is laid 
in one pan, and the equilibrium restored by 
putting any convenient substance, as sand, 
into the other. The bar is then removed, 
and ounce weights put in its place, which will 
be the exact weight of the bar, all errors of 
the apparatus being corrected by counter¬ 
poising, which will be evident to the reader 





412 


MANUAL OF A SSA YING. 


without further explanation. Of course the 
ounce weights must be proved by experiment 
to be correct among themselves. 

It is sometimes impossible to obtain troy 
ounce weights, in which case avoirdupois may 
be used. The same rule as to accuracy applies 
equally to them. Each pound equals 14.5833 
troy ounces. An excess of even pounds must 
be made with ounces and decimals, which can 
be prepared by any person of moderate me¬ 
chanical skill. The value of an avoirdupois 
ounce is 0.911458 ounce troy, or one-sixteenth 
of a pound. To make the calculation, it is 
only necessary to multiply pounds by the 
former and ounces by the latter factor, and 
add the two together. The following table 
may be used to facilitate the calculation: 



APPENDIX. 


413 


A voirdupois. 


Troy Ounces. 

A voirdupois . 


Troy Ounces. 

I 

ounce 

— 

o. 9 TI 45 8 

!3 

ounces 

— 

11.848958 

2 

ounces 

— 

1.822916 

14 

u 

— 

I 2.760416 

3 

<< 

— 

2-734374 

*5 

a 

— 

i 3 - 6 7 i 8 74 

4 

ii 

— 

3 - 645 8 33 

1 

pound 

— 

I 4.583333 

5 

a 

— 

4 - 55729 1 

2 

pounds 

— 

29.166666 

6 

u 

— 

5.468749 

3 

ii 

\ 

43-749999 

7 

ii 

— 

6.380208 

4 

ii 

— 

58.333333 

8 

a 

— 

7.291666 

5 

u 

— 

72.916666 

9 

(< 

— 

8.203 12 4 

6 

ii 

— 

87499999 

10 

a 

— 

9 - ii 45 8 3 

7 

ii 

— 

102.083333 

11 

u 

— 

10.026041 

8 

u 

— 

116.666 666 

12 

u 

— 

10-937499 

9 

u 

— 

I 3 I - 2 49999 


Suppose the bar to weigh twelve pounds 
and nine ounces; set the figures down thus: 

10. pounds. 

2. pounds. 

.9 ounces. 

12.9 

Look for 10 pounds in the table, which will 
be the same as 1 pound with the decimal 
point moved one place to the right, 145.833; 
opposite 2 pounds will be found 29.166; 9 

ounces will be found to be 8.203, which are to 
be added as follows: 





414 MANUAL OF ASSAYING. 

io. pounds. i45- 8 33 

2. pounds. 29.166 

.9 ounces. 8.203 


12.9 weight of the bar. 183.202 troy ounces. 

When decimals of an ounce are calculated, 
the values may be taken from the first column 
of the table. Suppose the decimal to be .7, 
or t 7 ¥ , move the decimal point in the seventh 
line one place to the left, and the result will 
will be .6380208, which is to be added to the 
sum of pounds and ounces. 

The above method of weighing is sometimes 
convenient in isolated mining localities, where 
no accurate bullion balance or large sets of 
Troy weights can be obtained. 

A table having been given to calculate Troy 
ounces from avoirdupois pounds, the follow¬ 
ing table has been prepared to reverse the 
operation, and it will in many cases be found 
convenient: 










APPENDIX. 


415 


TABLE FOR CHANGING TROY OUNCES TO POUNDS AND 

DECIMALS AVOIRDUPOIS. 


Troy Pounds 

Ounces. Avoirdupois. 

1 .06857 

2 .I37I4 

3 .20571 

4 .27428 

5 .34285 


Troy Pounds 

Ounces. Avoirdupois. 

6 .41142 

7 . 47999 

8 .>.54856 

9 .61713 


Gold is always estimated in troy ounces and 
decimals. A convenient set of weights may 
be constructed as follows : 


Ounces. Decimals. 

500.o .500 

300.0.300 


.. 

t no. 



. 0 .oso 

. 

20. 



Ounces. 

Decimals. 

TO . 


IO. 


5 . 

• 

• 

• 

• 

• 

• 

0 

• 

0 

0 

Ol 

2. 


• 

2. 


1 . 



Estimation of the Value of the Bar .— Sup¬ 
pose the total fineness (silver and gold) to 
be 900, and the fineness of gold as found 
by assay to be 100; by subtracting the latter 
from the former the fineness will be found to 


























416 


MANUAL OF ASSAYING. 


be 800. Now, as one ounce of pure gold is 
worth $20.6718, one one-thousandth will be 
worth $0.0206718; therefore, an ounce of 
alloy, containing 100 parts of pure gold, would 
be worth $o.02o6o7i8x 100, or $2.06718. The 
last three decimals may be disregarded, unless 
the bar is very large. 

The value of the silver is obtained in the 
same way. An ounce of pure silver is worth 
$1.2929, and one one - thousandth equals 
$0.0012929. This multiplied by the fineness 
of silver as found, would give the value of the 
silver in each ounce of the bar. 

Multiplication may be avoided, and the cal¬ 
culations facilitated, by the employment of the 
following table : 



APPENDIX. 


417 


TABLE FOR DETERMINING THE VALUE OF GOLD AND 

SILVER BULLION. 


Fineness . 

Gold . 

Fineness . 

Silver . 

.000J... 

. .010335917312 

.OOO^ . 

.. .000646464646 

.001 ... 


.OOI .. 


.002 ... 

• -041343669250 

.002 .. 

.. .002585858584 

.003 ... 

. .062015503875 

.003 .. 


.004 ... 


.004 


.005 ... 

• -103359173125 

• 

0 

0 

c_n 

• 

• 


.006 ... 


.006 .. 

•• -007757575752 

• 

• 

O 

O 

• 

. .144702842375 

.007 .. 

.. .009050505044 

.008 ... 

• -16537467700° 

.008 •• 

.. .010343434336 

.OO9 ... 


.OO9 .. 



The manner of using this table is the same 
as a similar one described : 

GOLD. 

100 same as 001, decimal two places right = $2.06718 
= value of gold per ounce. 

SILVER. 

800 same as 008, decimal two places right = $1.03434 
= value of silver per ounce. 


Value of gold per ounce.$2.06718 

“ silver “ . 1-03434 


Total value per ounce 


$3.10:152 



























41B 


MANUAL OF ASSAYING. 


These results, multiplied by the number 
of ounces and decimals of an ounce the bar 
weighs, would be its value in dollars and 
cents. Suppose the bar weighed 1,540.6 
ounces, then — 

$2.06718x1,540.6= $3,184.69 

1-03434X1,540.6 = 1,593-5° 

Total value of the bar = $4,778.19 

Stamping the Bar .—The assays being com¬ 
pleted, the bar weighed, the calculations made, 
and values ascertained, there remains only to 
stamp the bar with the proper steel dies, giv¬ 
ing the following data, which must be im¬ 
pressed in the bar before it can be sold : Num¬ 
ber of the bar (which is the number of the 
assay also); name of assayer; the total weight 
of the bar, given in Troy ounces and decimals; 
fineneas of gold; fineness of silver; total value 
of the bar in dollars and cents ; date. 

IX. THE ASSAY OF BASE BULLION. 

The uncertainty in the assay of base bullion 
lies, not in the determination of the amounts 




APPENDIX . 


419 


of gold and silver present, but in the difficulty 
of obtaining an average sample. 

This question has given rise to an amicable 
discussion in the columns of the Engineering 
and Mining Journal , between various parties 
interested (issues of May 20, June 3, July 1, 
and September 9, 1882), eliciting some valua¬ 
ble information, which I purpose to reproduce 
herewith. 

A base bullion may contain lead, silver, 
gold, copper, arsenic, antimony, and perhaps 
other metals, and sulphur. When this is 
melted and cooled, it tends to form alloys of 
varying degrees of fusibility, which with the 
dross or scum (a mixture of oxides, sulphides, 
etc.) make a pig or bar, from which it is not 
an easy matter to select a fair sample for 
assay. 

In many smelting establishments the sur¬ 
face of the melted bullion is skimmed, and 
the clear lead ladled into the mould, till the 
latter is filled to within an inch of the top, 
and when it has solidified, the mould is filled 



MANUAL OF ASSAYING. 


420 

completely. There results then a nice-look¬ 
ing bar, composed of good lead above and 
below, with much dross in the centre. This 
would not matter so much if an equal portion 
of the dross could be gotten at for assay; but 
there’s the rub. The ordinary way of chip¬ 
ping the top and bottom of the bar does no 
good, since it seldom cuts deeper than i inch 
below the surface. Even a punch cutting a 
chip |- inch deep does not solve the problem, 
for it will not reach the dross when cast in the 
middle of the bar. 

Mr. L. S. Austin, in the issue of Septem¬ 
ber 9 of the journal quoted, suggests a 
method which seems to meet the requirement. 
“ It consists in the use of the punch which I 
have already described [June 3d issue], and 
which takes a chip of about inch in diam¬ 
eter and uniform in thickness. It is driven 
clear in to one-half the depth of the bar by 
the use of a sledge. The bar being, say, four 
inches in depth, a chip a little over two inches 
long is then taken both from top and bottom 





APPENDIX. 


42 I 

of the bar. The chip is then slipped into a 
hole bored two inches deep into a block, and 
the projecting lower end trimmed off with 
shears to the exact length of two inches. 
Each chip represents, consequently, one-half 
the bar, its companion representing the other 
half; moreover, each chip is of the same 
weight. Thus each bar is represented accord¬ 
ing to its relative weight and to its entire 
depth.” 

Having obtained these chips, they are next 
melted, and poured into a small mould. Take 
this sample bar, cut slices across, each slice 
being a section of the bar. Cut from these 
slices i A. T. for assay. By running five of 
these \ A. T. assays, and uniting the silver 
beads obtained, for parting, the gold present 
can be accurately determined. 

Cupel the samples, “feathering” the cupels. 
Brittle or hard bullion can be scorified first, if 
necessary. 

Consult the numbers of the journal re¬ 
ferred to. 



422 


MANUAL OF ASSA YING. 


X. QUALITATIVE TESTS. 

I have thought it a good plan to give a few 
simple wet tests for some of the metals, and 
acids united with them, as found in ores. 

Ordinarily these tests work better on the 
powdered ore, though sometimes, as will be 
mentioned, the original rock can be directly 
treated. 

Carbonates .—Place a drop of any strong 
acid upon the suspected rock ; if effervescence 
(or boiling up) ensues, unaccompanied by 
. any odor, it contains carbonates. This test 
does not always show well with small quanti¬ 
ties of carbonates; try then some of the 
powdered ore with acid in a test-tube. To 
confirm the presence of carbonic acid, suspend 
in the test-tube a glass rod that has previously 
been dipped in lime-water; the drop on the 
rod should become turbid or milky, owing to 
the formation of carbonate of lime. 

Place a small sample of the pulverized ore 
in a test-tube, add to it some nitric acid, a 
little more than will cover it, and heat till the 



APPENDIX. 


423 


acid does not seem to dissolve any more of 
the ore ; let cool, after which add as much 
pure water as there is acid, and shake. 

Filter, in manner described under “Copper 
Analysis,” p. 349. 

Sulphates .—To some of the filtered acid 
solution add solution of chloride of barium 
(or, if lead be present, of nitrate of barium). 
A white cloudiness or precipitate (which does 
not instantly form in dilute solutions) shows 
the presence of sulphates. 

Sulphides .—To a piece of the rock, or to 
some of the powdered ore, add a drop of 
nitric acid. If sulphides are present in any 
quantity, a strong odor, similar to that of rot¬ 
ten eggs, will be given off. 

Tellurides .—Take a small piece of the ore 
and place it on the cover of a porcelain cap¬ 
sule, and heat with the inner flame of the 
blow-pipe for a couple of minutes. Now place 
a drop of concentrated sulphuric acid on the 
cover, and let it slide down to the heated 
fragment. As soon as it touches or ap- 





424 MANUAL OF A SSA YING. 

proaches very near the ore a beautiful carmine 
coloration forms, strongly contrasting with the 
white porcelain. As the latter cools, the 
color fades. Any white crockery, as a piece 
of a broken plate or saucer, will do to use in 
this test. 

Copper .—To a piece of the rock on a white 
porcelain surface add a few drops of nitric 
acid and stir. Add now an excess of ammo¬ 
nia water. If the mass turns blue, copper or 
its compounds is undoubtedly in the ore. If 
the latter contains much copper, a polished 
knife-blade dipped in an acid solution of it 
will receive a coating of metallic copper. 

Iron. — If, at the same time the solution 
treated with ammonia turns blue, or even if it 
does not do so, there appears on the porce- 
lain or in the test-tube, a reddish-brown gelat¬ 
inous mass, then iron is present. 

As further tests for iron, on one part of an 
old plate put a crystal of sulphocyanide of 
potassium and on another a lump of ferrocya- 
nide of potassium (yellow prussiate of potash); 






APPENDIX. 


425 


now pour on each a little of a hydrochloric acid 
solution of an ore containing iron ; a blood-red 
coloration with the first-named re-agent, and a 
magnificent blue precipitate with the second, 
prove conclusively the presence of iron com¬ 
pounds. Of course these tests can be shown 
with the filtered solution in test-tubes. 

Lead .—Drop a little nitric acid upon a piece 
of ore supposed to contain lead, then add a 
little water, and finally a crystal of iodide of 
potassium. A bright-yellow precipitate will 
form if lead is present. 

Manganese .—The best and simplest test for 
manganese is to fuse the substance with a 
little carbonate of soda and nitrate of potash 
on a strip of platinum in a hot flame. The 
manganese unites with the sodium, forming 
green manganate of soda. T he manganese 
may have to be separated from other matters 
in a manner similar to the method given under 
the crucible process, p. 255. 

Silver .— If this metal is in any appreciable 
quantity in an ore, it will dissolve in nitric 





426 


MANUAL OF ASSAYING. 


acid (excepting the chloride ores). To the 
acid solution add a little hydrochloric acid, 
solution of common salt, or even a dry grain 
or two of the latter. A curdy, white precipi¬ 
tate of chloride of silver is thrown down, 
which is not soluble in water (as is chloride 
of lead, on the contrary), but dissolves easily 
in ammonia water. The precipitate turns 
black on being exposed to light. 

As stated above, chloride ores do not dis¬ 
solve in nitric acid ; therefore, when they are 
suspected to be present, put some of the pow¬ 
dered ore into a small bottle, pour in a small 
quantity of very stong ammonia water, cork 
up the bottle, and let it stand for a few hours. 
Then add, in slight excess, nitric acid. The 
white precipitate of silver chloride will at once 
come down if there is any in the ore. 

The best test for gold is the fire assay. To 
learn the colors and appearances of the tests 
above given, try them on the following sub¬ 
stances : 



APPENDIX. 


427 

Carbonates.Bi-carbonate of Soda. 

Sulphates.Sulphuric Acid. 

Sulphides.Copper or Iron Pyrites. 

Tellurides.Any Telluride Ore. 

Copper.Copper Wire. 

Iron.Nail or Wire. 

Lead.Sheet Lead or Galena. 

Silver.Silver Foil and Horn Silver. 

Manganese.Black Oxide of Manganese. 


Consult the books on qualitative analysis 
for further information or tests. 

XI. BRIEF SCHEME FOR SILICA, IRON, AND 

MANGANESE. 

It is very often the case that the percent¬ 
ages in an ore of the above-mentioned sub¬ 
stances are wanted. More particularly is this 
true with carbonate ores. Hence the follow¬ 
ing notes : 

Dissolve the weighed ore in hydrochloric 
acid by the aid of heat. Filter hot, and wash 
with hot water. The filtrate contains the iron, 
with chloride of lead, etc. 

The silica on filter contains chloride of lead. 












428 MANUAL OF A SSA YING. 

Wash this out with hot solution of citrate of 
ammonium, following with hot water. Ignite 
the silica while still damp. 

To the iron in solution in the filtrate add 
sufficient sulphuric acid to convert all the lead 
into sulphate of lead. Warm the solution, if 
not already so, and add, drop by drop, dilute 
stannous chloride solution, until the liquid be¬ 
comes colorless, showing that the iron is all 
reduced to state of protoxide. Avoid a great 
excess of the tin solution. Now cool, and add, 
all at once , an excess of strong mercuric chlo¬ 
ride solution. The precipitate formed should 
be perfectly white. If dark-colored, it indi¬ 
cates that insufficient mercuric chloride has 
been used, and the analysis is spoiled. If the 
precipitate is all right, the solution is ready 
for titration with standard bi-chromate of 
potash solution. (Consult Presenilis’ “ Quali¬ 
tative and Quantitative Analysis,” and Hart 
and Sutton on “Volumetric Analysis.”) 

For manganese in ores (excepting silicates), 
heat a weighed sample in crucible in open fire 





APPENDIX. 


4 2 9 


for fifteen minutes, converting the manganese 
into protosesquioxide of manganese. Treat 
with hydrochloric acid, and titrate with iodide 
of potassium and hyposulphite of sodium. 
(See Sutton.) 

XII. DETERMINATION OF MOISTURE IN AN ORE. 

It is often a matter of importance to know 
the amount of moisture or water contained in 
an ore. The simplest manner in which to de¬ 
termine this, and a satisfactory one at that, is 
to sample out a certain weight, say five 
grammes , and transfer to a porcelain capsule, 
the weight of which is already known. Ex¬ 
pose the capsule and contents to steam heat, 
in any convenient way, for one-half hour, then 
weigh. Heat half an hour longer and weigh 
again. There should be but a slight differ¬ 
ence in the last two weighings. The difference 
between the last weight and the original 
weight of dish and ore is the loss by driving 
off the water ; this difference divided by the 
amount of ore taken, and multiplied by ioo, 
is the percentage of moisture in the ore. 



430 


MANUAL OF ASSAYING. 


XIII. DETERMINATION OF SULPHUR IN PYRITES. 

Weigh i gramme (or say io grains) of the 
finely powdered ore into a casserole ; add a 
small amount of chlorate of potash, cover 
with watch glass, add 50 c.c. concentrated 
nitric acid, and heat to boiling, adding a little 
more chlorate from time to time. When per¬ 
fectly oxidized, remove watch glass (and it 
should be rinsed into the casserole), and evap¬ 
orate to small bulk on a water bath. Add a 
little strong hydrochloric acid, and evaporate 
to dryness, moisten with the same acid, add 
water and filter from silica and the gangue. 

To the filtrate add 1 gramme (or 10 to 15 
grains) tartaric acid, heat, add hot solution of 
baric chloride, drop by drop, boil, let settle, 
filter and wash well with hot water. 

Weigh a clean porcelain or platinum cruci¬ 
ble, add filter and precipitate, burn to ashes, 
cool, weigh as baric sulphate: after deducting 
weights of crucible and filter ash, multiply 
remainder by 0.1374, and the product by 100 
or 10 for percentage of sulphur. 



APPENDIX. 


431 


XIV. THE ASSAY OF TIN ORES. 

In order to make an accurate fire-assay of 
a tin ore, it is necessary to bear in mind sev¬ 
eral things. First, that the cassiterite or tin 
oxide is itself a small percentage of the ore ; 
secondly, that the other matters present tend 
to prevent an accurate result; it is therefore 
essential that the tin ore should be previously 
concentrated and purified. 

Prep dilation of the Sample .—Weigh say 50 
lbs. of the ore, and remember that the result¬ 
ing “concentrate’’ is to be also weighed, so 
that we may know its proportion to the orig¬ 
inal ore. Crush, by means of hand crusher, 
motar and rubbing plate until the whole, save 
the mica, will pass through a 20-mesh sieve. 
Examine the mica for any attached mineral, 
remove by grinding and screening and add to 
the first lot screened. The mica is to be 
rejected. “Pan” the screenings, being care¬ 
ful that the tailings do not contain any 
tin. 

The above treatment gets rid of about all 




432 


MANUAL OF ASSAYING. 


impurities save garnets, sulphides and selen- 
ides. Roast the concentrates in a roasting 
dish as usual, and after roasting, chill in cold 
water. Boil the roasted ore in a porcelain 
dish with nitro-hydrochloric acid (removing 
iron), wash off acid and any light particles, 
dry and weigh. If, for example, the 50 lbs. 
of ore should produce y 2 pound of finally puri¬ 
fied ore, it would represent 1 per cent, of the 
original ore. The next step is to ascertain 
how much metallic tin the supposed tin oxide 
contains. 

Make up the following 

CHARGE. 

Ore ... 10 grammes or 160 grains. 

Cyanide of potash. 40 “ “ 640 grains. 

Use size “J” crucible, ram 5 grms. (80 
grains) cyanide of potash in bottom, then the 
charge, lastly 5 grms. cyanide as a cover, 
us ng no salt. Time, 15 minutes. 

The fire should be hot and ‘ ‘ kept at the 
highest point to which the cyanide can be 
heated without beginning to boil or to evolve 






APPENDIX. 


433 


heavy fumes. An assay may be considered 
finished when the pure upper slag has become 
so transparent that the impurities contained at 
the bottom of the crucible are visible through 
it. The tin will then have collected into one 
button beneath the lower slag, and very few, 
if any, frills will be found.”—( Hoffmann .) 

The assay of a tin ore needs much care and 
practice, and the cyanide should be the best 
grade (98 per cent.) for, although this is ex¬ 
pensive, its use will give the most accurate 
results. 

Assayers and others especially interested 
in tin ores will find a most exhaustive and in¬ 
teresting letter on “The Dry Assay of Tin 
Ores,” by Prof. H. O. Hoffmann, which was 
read at the Colorado meeting of the American 
Institute of Mining Engineers, June, 1889, and 
given in the Technology Quarterly, Vol. 3, 
No. 2, and in the Chemical News, in the Nos. 
ranging from Aug. 1, to Dec. 26, 1890, from 
which article this chapter is chiefly ex¬ 
tracted. 




434 


MANUAL OF ASSAYING. 


XV. GOLD AND SILVER ORES AND MINERALS. 

I. How to find them. 

II. How to know them. 

III. How to vahie them. 

IV. How to treat them. 

I. How to find them. 

A careful study of the entire subject of gold 
and silver ores and minerals should start at 
the very beginning. This means then, first, 
a little knowledge of Geology in general, and, 
to learn how these ores and minerals came to 
be deposited in their several places, necessi¬ 
tates the study of Geology in particular, 
namely: the formation of ore deposits. The 
would-be prospector can do no better with his 
spare winter evenings than to occupy them in 
reading the authorities on page 474, in per¬ 
haps the following order: Dana (text-book), 
Rutley, and Von Cotta, in full, and referring 
to Dana (manual), Le Conte, and to such 
other kindred books as the judgment selects, 
for special information on ore deposits. 

The above for the winter. In the spring 





APPENDIX . 


435 


the prospector wants to get into the mountains. 
A useful little work to read just before starting 
is Pomeroy’s Mining Manual for Prospectors 
and Miners (page 477 this book"). Note 
especially his “Camp Outfit for Three,” on 
page 69. 

Arriving at his destination, the prospector 
begins his search. The following article on 
“ How to Prospect,” copied from Wilson’s 
Mining Laws (originally in Blake’s Handbook 
of Colorado) will be good, seasonable advice, 

and read in connection with what Pomeroy 

% 

says on “ Prospecting,” page 58, will give him 
considerable aid: 

1. Examine the gravel and boulders of the mountain 
streams, and note carefully the structure and character 
of the gravel wash. This will reveal the geological 
formations that are intersected by the stream. Try 
the sands at the head of the gravel bars for free gold,* 
or for anv crystallized mineral If the structure of the 
quartz boulders or other vein stones is favorable, go up 
the stream until the geological zone is found that has 
produced the quartz or other metal-bearing minerals. 
Then follow the supposed metal-bearing zone on its 


*See “ Pan Test for Gold” ( “ Panning” ), on page 369.—(W. L. B.) 







436 


MANUAL OF ASS A TING. 


line of strike,* and make especially careful examina¬ 
tions wherever eruptive dykes are found intersecting 
the formation. 

2. When a lode or vein is found, note carefully its 
relation to the country rock, especially any differences 
in the opposite walls of the vein. Then follow it on 
the line of outcrop and note carefully those points 
where the best f ores are seen, so as to determine the 
position of the best ore chutes before making any loca¬ 
tion on the lode. 

3. The first work should consist of shallow cuts 
across the lode at intervals of 50 to too feet, or if the 
vein is small and partially covered by soil and debris, 
a trench along the line of out-crop is preferable. If 
the surface tracing is satisfactory, and the true line of 
strike has been determined, then survey your claim and 
stake off the boundaries according to the requirements 
of the United States laws. J 

4. The work of exploring the vein under ground is 
the next thing in order. To do this intelligently you 
must select that point on the line of outcrop where the 
best ore is found, then sink a shaft on the lode, follow¬ 
ing the angle of dip, keeping both foot-wall and hang- 

* Glossaries of terms used in geology, mineralogy, prospecting, mining, 
metallurgy, etc., will be found in Pomeroy’s Mining Manual (pp. 72-9) 
Copp’s Mining Code (pp. 88-125, by R. W. Raymond), Collins’ First Book in 
Mining and Quarrying (pp. 101-114), Phillips’ Explorers’ and Assayers’ Com¬ 
panion (pp. 428-468), Dana’s Manual of Mineralogy (pp. vii-xii), and Ander¬ 
son’s Prospector’s Handbook.—(W. L. B.) 

f Confirming such observations by assays.—(W. L. B.) 

t Pomeroy (pp. 80-116), also note list of books on Mining Law, in ap¬ 
pendix (pp. 435-6).—(W. L. B.) 







APPENDIX. 


437 


ing-wall exposed if possible. If the lode is too wide 
for this to he done, then follow the best ore streak of 
the vein itself, and at every fifty feet in depth make 
cross-cuts to the walls of the vein. 

5. After a 100 feet deep shaft has been reached, run 
levels each way from the shaft on the line of the vein 
in order to determine the extent or spread of the ore 
chute or chimney on the horizontal line. When the 
limit of the ore body on the horizontal line has been 
ascertained, then sink 100 feet more and drift right and 
left as before. If more than one chimney of ore is 
found on the line of the vein, a shaft should be sunk 
on it, and drifts run as above stated, being careful to 
confine all the exploring work within the walls of the 
vein itself. * 

6. When enough has been done to prove the char¬ 
acter, size and quality of the vein, it will then be time 
to determine the portion, character and extent of the 
“dead-work” necessary to work the mine to the deep. 


^Concerning the “sampling” of a vein or the side walls of a tunnel or 
indeed of any part of a mine, which may be well to have done frequently, 
proceed as follows: On a distance, say of 300 feet, divide the exposure into 
three sections of 100 feet each. Then taking a certain height from floor of 
tunnel, conveniently breast-high, chip continuously pieces in a vertical width 
of from 3 to 6 inches, letting the pieces drop onto paper or bagging spread on 
the floor of tunnel at bottom of side wall, and so go along the entire 100 feet. 
The three or four hundred pounds thus obtained, will represent a fair average 
of all veins vertically crossing the wall, and are to be crushed and averaged 
down as usual. And the same with the remaining two sections of 100 feet 
each. By such sampling, the miner will be sure to get at least portions of 
any rich veins or masses exposed. Should one section show up especially 
well, divide that section in halves, and sample again. By such a series of 
eliminations, a rich “find” may be discovered, where a mere hand-picked 
specimen might miss it altogether. Above all, beware of the “ salting" of a 
mine, by interested persons. A word to the wise is sufficient.—(W. L. B.) 







MANUAL OF ASSAYING. 


438 

These questions should be settled by careful surveys 
made in the light of all the local facts and surroundings, 
such as the geological structure of the country rock, the 
probable amount of water to be raised, the lowest point 
of drainage by adit or level, and the most convenient 
point of delivery of the ores to the surface, etc. 

The last part of the preliminary exploration of any 
mine is to determine, by actual tests, what are the best 
methods of reduction,* and the extent and kind of re¬ 
duction works needed, etc. 

7. After all the preliminary facts have been thor¬ 
oughly ascertained and clearly defined, the unavoidable 
risks of mining- will have been fully met and overcome. 
All subsequent operations are simply matters of skill 
and business management, and the capitalizing of the 
mine becomes a mere matter of business detail. 

The requirements are as follows: 

1. The preliminary exploration must have ore 
enough cut and under-run, or otherwise exposed, to 
give at least two years’ work for reduction work of an 
extent sufficient for the annual average out-put of ore. 

2. The reduction works must be suited for the best 
treatment of the ore. 

3. The exploration of the mine must be pushed 
ahead of the extraction of ore, so as to expose at least 
one ton of ore in new ground for every ton extracted 
from the previously exposed ground. 

4. Before erecting reduction works, the exposed ore 


♦See Section 4, “ How to Treat Them.”—(W. L. B.) 






APPENDIX. 


439 


in the mine should be so thoroughly tested as to guar¬ 
antee a net profit to pay the whole cost of such work. 

5. The mine being well opened, and the reduction 
works, or plant, established, the general success of the 
enterprise must depend upon the efficiency of the gen¬ 
eral business management. 

A little pamphlet by F. L. Bartlett, entitled 
“ Minerals of New England, Where and How 
to Find Them,’’ while somewhat local, is not 
enough so to prevent it giving fair descriptions 
of the minerals found elsewhere, with tests 
for the same. See also, “Underground Treas¬ 
ures: How and Where to Find Them,” by 
Jas. Orton, and “The Prospectors’ Hand¬ 
book,” by J. W. Anderson. 

II. How to know them. 

That science which covers the knowledge of 
rocks is termed Lithology, that which concerns 
minerals is mineralogy; while crystallography 
restricts itself to the specific structure of rocks 
and minerals. The study of the above three 
branches of exact science gives the theoretical 
knowledge which is to be transmitted into 
practical results by aid of actual work in blow- 






MANUAL OF ASSAYING. 


440 

pipe analysis and determinative mineralogy, 
combined with qualitative and quantitative 
analysis. 

All this seems formidable enough, but no 
one can become a thorough expert, unless he 
does understand well the above named 
branches, hence it means patient study, long 
practice and a certain amount of manipulative 
skill. But even a smattering of all of the 
“ologies” outlined, will not injure the miner 
or prospector, and is sure to help him. There 
is no royal road to learning these sciences, but 
attention, observation, experience and experi¬ 
menting will ultimately enable him to learn 
very much about the nature of ores and min¬ 
erals. 

Gold and silver, one or both, occur free or 
in combination, or associated with many rocks, 
ores and minerals. The following list gives 
a slight idea of the universal distribution of the 
precious metals in and among other minerals, 
ores and rocks:* 


*See lists pp. 181-4, also pp. 461-5 in Appendix 









APPENDIX. 


441 


Aikinite, algodonite, altaite, anatase, apatite, 
argillaceous schist, arsenopyrite, asbestos, 
barnhardite, barytes, beresite, beryl, bismuth- 
inite, bismuth ores, blende, bornite, boulanger- 
ite, brookite, calcite, cerussite, chalcopyrite, 
chlorite, chloride - schist, chloro-arseniate of 
lead, chrome-iron, chrysocolla, copper ores 
generally, copper pyrites, corundum, cuprite, 
diamond, diorite, emerald, enargite, feldspar, 
ferro-tellurite, fluor-spar, galena, garnet, gneiss, 
granite, heavy-spar, hematite, horn-blende, 
horn-blendic schist, iridosmine, iron oxides, iron 
pyrites, itacolumite, joseite, kyanite, leucopy- 
rite, magnesite, magnetite, malachite, man¬ 
ganese oxides, melaconite, mica slates, mime- 
tite, mispickel, molybdenite, monazite, native 
antimony, native arsenic, native bismuth, na¬ 
tive copper, native mercury, native palladium, 
native platinum, native tellurium, porphyry, 
pyrite, pyrites of various kinds and mixtures, 
pyrrhotine, quartz, realgar, red and brown 
hematites, red oxide of copper, rhodium, ruby, 
rutile, sapphire, scheelite, selenpaladite, ser- 



442 


MANUAL OF ASS A TING. 


pentine, siderite, smaltite, sphalerite, spinel, 
steatite, stibnite, talc, talcose-schist, tellurite, 
tellurium ores, tellurpyrite, tenorite, tetrady- 
mite, tetrahedrite, tinstone, titaniferous iron, 
topaz, tourmaline, trap rock, wehrlite, zinc- 
blende, zircons. 

But the miner holds in his hand a piece of 
ore and wants to know the probabilities. What 
are they? Aside from actual tests, all that 
can be given are hints and suggestions, indicat¬ 
ing the probabilities. If the sample is very 
heavy, look out for lead (it might also be an 
ore of mercury, or common barytes), and if 
also it is yellowish, it is pretty sure to contain 
lead. If moderately heavy and is yellowish, 
brownish or reddish in color, there is undoubt¬ 
edly iron present. If very black, probably 
manganese. If blue or green, suspect copper 
(a very light green, certain arsenic ores). 
The above describes the specimen when it is 
of a dull , earthy appearance. If, however, it 
is shiny and light yellow (brassy), it will be or 
contain iron pyrites; if of a more golden yellow, 



APPENDIX. 


443 


or of a rainbow shimmer, then copper pyrites; 
if leaden, there is galena, if whitish lead 
color, blende. Examine ores and minerals 
known to be those named above, and remem¬ 
ber their characteristics. And further, try to 
confirm your suspicions by the simple tests 
given on pp. 422-427 in the appendix. Metal¬ 
lic silver and gold are too well known, even to 
the ignorant, to be mistaken for other metals, 
but by crushing and panning, or by fusing in a 
crucible according to processes described in 
the chapter on assaying, all doubt will be re¬ 
moved. 

And this is about all that one can say in try¬ 
ing to teach the nature of a gold and silver ore 
by simple observation only, without the cor¬ 
roboration of the blowpipe, the test-tube or the 
crucible. 

III. How to value them. 

The most common, if not the very first 
question put to the assayer (and one which he 
is expected to answer at once), is: “What 






444 


MANUAL OF ASSAYING. 


will it carry ? ” referring to the gold and silver 
value of an ore or mineral, A very easy ques¬ 
tion to ask — an exceedingly difficult one to 
answer. 

Of course the only accurate answer is that 
given by a careful assay, but what can we say 
without first using this infallible test? The 
specimen may belong in one of two divisions; 
it may be a typical gold or silver mineral, or 
an ore of a class known to often carry the 
precious metals. 

Thus, of the first class, the sample under 
discussion may be free gold in some one of its 
various forms, native silver, ruby silver, horn 
silver, silver-glance, etc. Now the mineralo¬ 
gist knows that if the mineral is pure silver- 
glance (with no gangue) it must contain 87 per 
cent, silver—over 25,000 ounces to the ton, 
(provided a ton of it were found); if it is pure 
horn-silver, which is 75 per cent, metal, then 
a ton of it would increase the wealth of the 
owner by nearly 22,000 ounces; the ruby 
silver, according to whether it was the dark or 






APPENDIX. 


445 


the light-red, the antimonial or the arsenical 
variety, would pan out in round numbers, from 
r 7,000 to 19,000 ounces per ton. 

If the sample is the pure mineral in a simple 
gangue, then the specific gravity will give the 
value. It is thus that free gold in quartz is 
sometimes estimated. 

If the sample is a mixture of various gangues 
and minerals, but still shows that it contains 
one or more of the valuable minerals men¬ 
tioned, then no exact figures of value can be 
given without an assay, but beforehand the 
comforting assurance can be truthfully put 
forth, that the ore is rich. 

But when we come to the second class, of 
ores proper, we are obliged to proceed very 
carefully. Among the most common sources 
of gold are the sulphurets of copper and iron, 
being iron sulphuret alone (iron pyrites) or 
copper and iron sulphuret (copper pyrites or 
chalcopyrite). We call either, when gold- 
bearing, auriferous sulpJmrets. The gold in 
these pyrites may vary in quantity from an in- 




446 


MANUAL OF ASSAYING. 


finitesimal trace, a practical nothing, up to 
many ounces per ton, and yet there be noth¬ 
ing on the surface to indicate the degree of 
richness. There is very little use in guessing 
the value of pyrites from its appearance only. 

The locality is a good indicator, but that 
often fails. If the pyrites was found in one 
of the gold-mining districts of the West, the 
South or even the extreme East, it may be 
valuable — it may likewise be worthless. But 
if found in other parts of the country, the 
chances are that the gold exists in too small 
quantity to be worked with profit. 

It is dangerous to generalize from specific, 
things, but I can not resist the temptation of 
saying, as drawn from my experience, with re¬ 
gard to these sulphurets, that nine out of 
every ten will be low in gold. 

In short, with any gold ores, unless the gold 
actually shows itself, beware of guessing at 
their value. 

With ores carrying silver, we have a little 
better chance. Galena, blende and “carbon- 




APPENDIX. 


447 


ate ores,” carry more or less silver. Concern¬ 
ing the last class, surface indications are worth 
but little. They resemble so many valueless 
earths, that an assay, only, can positively de¬ 
termine their value. Blende (or zinc sul- 
phuret or “blackjack”) seldom bears much 
silver. And more, I have found that ores that 
contain much blende, no matter what other 
minerals are present, do not often run rich in 
silver. 

Galena is rather a perplexing mineral, so 
far as it shows or does not show silver. The 
old theory that a fine-grain or “steel” galena 
was invariably rich, and a coarse-grain poor, 
is now pretty well exploded. The fine-grain 
is as often poor as rich, and the coarse-grain, 
instead of being low in silver, may mount up 
into the hundreds. Study a piece of galena, 
and see if it possesses any one of the three fol¬ 
lowing characteristics: 

ist. Does it have a peculiar bluish-purple 
lustre ? 

This lustre, difficult to describe in words, is 




448 


MANUAL OF ASSAYING. 

easily perceived, and is entirely different from 
the ordinary leaden shimmer of pure galena. 
The ores possessing it are pretty sure to be 
rich. 

2d. Does it have a smooth, almost curving 
surface, an appearance not unlike plumbago, 
and yet, at the same time, appears as if one 
could run his knife-blade just under the surface, 
and raise up a scale, as of mica, but yet one 
cannot? 

Such ores are invariably rich. 

3rd. Does it show, perhaps in the cleavage, 
a greenish coloration, more or less distinct? It 
will be rich. It does not follow that the 
silver is in combination with the galena; it 
may be a distinct mineral simply in the galena. 
But this is immaterial. The galena, as an 
ore, is rich, and that is the vital point. 

Furthermore, galena in a siliceous gangue is 
much more likely to be rich than that which 
is in a lime-stone (calcite) gangue. 

Gray copper (tetrahedrite) is a convenient 
name, applied, ordinarily, to any gray mixture 







APPENDIX. 


449 


of sulphurets. Rich or poor, in either gold or 
silver, it puts outside no sign of its varying 
possibilities. 

Here, then, we have opinions based largely 
upon experience, upon the characteristics of 
minerals which have shown by assay tests that 
they are what these indications have pointed 
out. 

IV. How to treat them. 

If the question which headed the last sec¬ 
tion, viz.: “What will it carry?” is the first 
one put to an assayer, the second one will 
surely be, “ How would you treat this ore? ” 
And this is even more difficult to answer at 
sight than was the first. 

Before undertaking to treat an ore, we 
should know four things: 

A. The assay value of an average of the 
ore. 

B. The nature of the metalliferous mineral 
or minerals containing the silver or gold, or 
both. 





45° 


MANUAL OF ASSAYING. 


C. The nature of the gangue. 

D. The relative proportions of the gangue 

$ 

and the metal-bearing minerals. 


A. The determination of the assay value 
of an average of the ore, or a mill-run checked 
by an assay will settle the question as 
to whether the ore is high grade or low 

B. The nature of the metalliferous mineral 
or minerals containing the silver or gold or 
both. 

The precious metals most commonly oc¬ 
cur in some one or more of the following 
groups: 



I. 

Free Milling Ores. -< 


1. Free gold and free 

silver. 

2. Chlorides, bromides, 

iodides or mixtures 
of them. 

3. Silver glance or sul- 

phuret of silver. 






APPENDIX . 


451 


II. 

Smelting Ores. 


< 


4. Oxides, carbonates, or 
mixtures of both, of 
lead, iron or copper. 
5= Sulphurets of iron, 
copper, or iron and 
copper or other mixed 
sulphurets (as gray 
copper). Also galena 
and blende. 

6. Arsenical and anti- 
monial ores (tellu- 
rides, selenides, etc.). 

There are other and rarer minerals not in¬ 
cluded in the above, but the classes are reason¬ 
ably complete. The classification is arbitrary, 
but the limits are not always sharp and clear, 
consequently it is not necessarily implied 
that any given ore must belong to but one of 
the divisions named. On the contrary, it may 
be of such complex nature as to belong to 
two or more, or even all six of the classes, 
consequently be both free milling and smelt¬ 
ing, and whether either free milling or smelt- 






45 2 


MANUAL OF ASSAYING. 


ing, it may contain representatives of the three 
classes included under the subdivision in ques¬ 
tion. 

C. The nature of the gangue. (See pp. 
239-242.) 

D. The relative proportions of the gangue 
and the metal-bearing minerals. 

General rule: “The heavier an ore, the 
greater the percentage of metalliferous min¬ 
eral; the lighter an ore, the greater the per¬ 
centage of gangue.” There are a few excep¬ 
tions to this rule. The chief one commonly 
met with is barytes or heavy spar, a gangue 
which is three-fifths as heavy as galena, the 
chief ore of lead. (Pp. 238-239). 

The relative proportions of gangue and min¬ 
eral determine whether or not an ore is to be 
concentrated. The eye tells something of 
these proportions, but a “panning” test will 
give quantitative results. 

The conditions of outlook have now been 
mentioned, uninfluenced by the questions of 




APPENDIX. 


453 


locality of the mine producing the ore, trans¬ 
portation, fuel, water, price of labor, etc. 
These, although very important, or indeed de¬ 
ciding whether or not an ore can be treated on 
the ground, will come in place later on. 

An inexperienced mining man may now say 
that it is all very well to make the distinctions 
drawn, but how is he to know the value of the 
ore, or the particular form of combination of 
the gold and silver, or the kind of gangue, or 
whether it is necessary to concentrate, etc. 
The only truthful answer that can be made is 
to assure him that in the long run it will un¬ 
doubtedly pay him to secure the services of 
those trained in the professions of mining en¬ 
gineering, metallurgy, assaying and chemistry, 
and who are devoting their time, brains and 
energies to such work. 

But either with or without such aid, there 
is no harm in his learning all he can about 
ores, and we will start out with an example, 
as being the simplest, most direct, and con¬ 
vincing of arguments. 





454 


MANUAL OF ASSAYING. 


Let him behold, then, quite a little lot of 
ore, representing a fair average of the product 
of the mine from whence it came, some of the 
pieces coming from just below the surface, 
others from varying depths in the vein. They 
also represent the width of the fissure, forcer- 
tain of the pieces are from next the hanging 
wall, certain from close by the foot-wall, with 
others from the centre of the vein. 

How shall we ascertain the nature of this 
ore? Long experience in the visual examina¬ 
tion of ores and minerals, blow-pipe tests, 
qualitative analyses, and assays will tell this. 
It is not to be expected that the ordinary min¬ 
ing man, or man of business who goes into 
mining, will know much about the latter 
branches of investigation (although even a 
slight acquaintance will benefit him). But as 
to the other qualification, the very word “ex¬ 
perience ” will show him how he will learn; by 
being told what any particular mineral is, and 
what any certain ore looks like, by a good 
memory, and a quick and searching eye; by 



APPENDIX. * 


455 

good use of his observant faculties, he will in 
time accumulate a vast amount of information 
which he can wisely supplement with a little 
study of the authorities. 

To return to the ore. This time it happens 
to be very simple in composition, being 
merely a quartz rock, deeply stained with 
reddish brown oxide of iron. Breaking open 
several lumps, and examining the interiors 
with a magnifying glass, shows no signs of 
sulphurets. These may have been, and prob¬ 
ably were once in it, but not at the present 
time—they have all been oxidized. Besides 
the iron oxides, it is probable that there is also 
a little carbonate of iron present, but that 
makes no difference. Further, it is possible 
that magnetic oxide of iron is present. Such 
an ore is typically gold-bearing. It may be 
rich (high grade) and show the gold. It may 
be rich and show none of the yellow metal. 
It may be poor (low grade). It may not con¬ 
tain even a trace of the precious metal. Here 
the eye ceases to be the arbitrator, and re- 






456 MANUAL OF ASSAYING. 

course viust be had to something more defi¬ 
nite in its verdict, and that is an assay. 

Moreover, if gold is present, the chances are 
that more or less silver will be associated 
with it. 

The average result of several careful assays 
gives an assumed mean of T W oz. of gold, 
and oz. of silver. With gold at $20.67, 
and silver at $1.29 the ounce, this ore would 
be worth $12.33 P er ton. The actual market 
value of the gold and silver would be even less 
than this, say $18 to $20 per oz. of gold, and 
silver according to market quotations on the 
day of sale. But, assuming the ore to be 
worth, as stated, $12.33, local circumstances 
will decide whether it is high grade or low 
grade. 

We have then ascertained the average 

O 

% 

amounts of gold and silver that are contained 
in the ore (and the hypothetical value which 
is to be calculated down to the market value), 
the nature of the mineral (i. e. free gold), and 
the nature of the gangue (i. e. iron-stained 





APPENDIX. 


457 


quartz). This is all we care about at pres¬ 
ent. 

The next point is the manner of treat¬ 
ment. The ore is essentially of the first class, 
that is, free milling, for there are in it no re¬ 
fractory minerals, as blende, pyrites, etc. 

The small amount of silver would seem to 
indicate that it is not present as a sulphuret or 
as some one of the chloride group (which fact 
could be settled by a careful analysis), hence 
the legitimate deduction is that both the 
precious metals exist at present in the free 
state, whatever they may have been previously. 
The metallurgical treatment then to be adopt¬ 
ed is that known as free milling, or direct 
amalgamation. Assays of the ore before amal¬ 
gamation, and of the tailings will determine 
the percentage of extraction of the gold and 
silver by the particular form of milling ma¬ 
chinery adopted. This percentage will serve 
as a check (it will be always higher) on the 
actual product obtained. 

But suppose that by visual examination or 





45§ 


MANUAL OF ASSAYING. 


by blow-pipe we learn that the sample con¬ 
tains sulphurets , as well as the iron oxides (and 
indeed it is very usual to find sulphurets ap¬ 
pearing in ores as the work progresses in or 
down, for the oxidation may be only at the 
surface), then what? Tests must show how 
much gold is free-milling, and how much 
passes away with the tailings (that is in and 
among the sulphurets). If the amount found, 
by frequent average tests, in the sulphurets 
will pay to work (and local conditions only 
can determine this), then smelting, preceded 
by concentration, must come in. The fol¬ 
lowing table is from an actual “milling test:” 



Gold, 

oz. 

Per Ton. 

Gold, 
Value 
Per Ton. 

Silver, 

oz. 

Per Ton. 

Silver, 
Value 
Per Ton. 

Total 
Value 
Per Ton. 

. Assay of the Ore. 

h 

$16.54 


$0.20 

$16.74 

Saved by Free 
Amalgamation. 


$14-25 

1 % 

$0.20 

$14.45 

Saved, per Ton of 
Original Ore, by con¬ 
centration to of 

1 per cent. 

1M0 

$ 0.24 

Trace. 


$ 0.24 

Passed into Tailings. 

10015 

$ 2.05 

Trace. 


$ 2.05 

Assay of Sulphurets. 

4 , 2 o 

$86.82 

i*o 

$0.20 

$87.02 






















































APPENDIX. 


459 

In general, such an ore as the above would 
pay to work. 

This is not a treatise on smelting, and we can 
give but a little advice: Get a man who un¬ 
derstands his business thoroughly, to manage 
your property, if it proves to be worth work¬ 
ing, and if the ores are complex. And what 
is here written with regard to iron oxides and 
sulphurets will be equally true of any other 
ores which are both free-milling and refractory. 

XVI. DETERMINATION OF SPECIFIC GRAVITY OF 

MINERALS. 

i st. By the balance .—Weigh a small piece 
of the mineral on a delicate balance, next 
place a little bench straddling the scale pan 
(without touching it) and on this set a small 
beaker of distilled water of a temperature of 
6o° F. Tie a piece of hair around the min¬ 
eral and suspend it in the Water from the scale- 
beam hook, so that mineral does not touch 
sides or bottom of beaker, shaking off all air 
bubbles and weigh again. Formula as fol¬ 
lows: 






460 


MANUAL OF ASS A TING . 


Weight of mineral in air= W 
“ “ “ “ water= JV 

. r W 

Specific gravity = w _-^ , 

2d. By 1 he flask .—Take a specific grav¬ 
ity flask, as shown in Fig. 131, and fill it with 
distilled water of 6o° F., so that 
when the stopper is squeezed in, the 
water will over-run through the nar¬ 
row opening at top, and weigh care- 

Fig 131* 

fully. Powder some of the mineral, 
empty a little of the water from the flask, pour 
in the powdered mineral, fill with water, 
tighten stopper as before, remove excess of 
water, and again weigh. In both weighings 
the bottle is “Tared” by an equal weight on 
the other scale-pan. 

Formula: 

Weight of mineral = W 

“ “ flask and water = W' 

“ “ flask, mineral and water = W" 

W 



Specific gravity = 


(W+ IV')—JV" 













SECTION II. 


LISTS AND REFERENCES. 

GOLD. 


LIST OF THE PRINCIPAL GOLD MINERALS FOUND IN THE 

UNITED STATES. 


NAME. 

1. Calaverite (telluride of gold). 

2. Gold amalgam. 

3. Electrum (argentiferous gold). 

4. Miillerite (telluride of gold, 
silver and lead). 

5. Nagyagite (black tellurium, 
foliated tellurium, telluride 
of gold and lead). 

6. Native gold (flour, leaf, wire, 
nugget, free, etc.). 

7. Petzite (telluride of gold and 
silver). 

8. Sylvanite (graphic tellurium, 
yellow tellurium, telluride of 
gold and silver) 


COMPOSITION. 

Gold, tellurium. 

Gold, mercury. 

Gold, silver. 

Gold, silver, lead, 
tellurium. 

Gold, lead, tellu¬ 
rium (antimony, 
sulphur). 

Gold. 

Gold, silver, tellu¬ 
rium. 

Gold, silver, tellu¬ 
rium (antimony). 


461 


462 


MANUAL OF ASSAYING. 


MINERALS LIKELY TO CARRY GOLD. 


I. 

Aikinite. 

% 

14. 

Magnolite. 

2. 

Altaite. 

i 5 - 

Melaconite. 

3 - 

Argentite. 

16. 

Native arsenic. 

4 -' 

Arsenopyrite. 

i 7 - 

“ bismuth. 

5 . 

Bismuthinite. 

18. 

“ silver. 

6. 

Chalcopyrite. 

19. 

“ tellurium. 

7 - 

Coloradoite. 

20. 

Pyrite. 

8. 

Ferro-tellurite 

21. 

Sphalerite. 

9 - 

Galenite. 

22. 

Tellurite. 

10. 

Henryite. 

2 3 - 

Tellurpyrite. 

11. 

Hessite. 

24. 

Tetradymite. 

12. 

Joseite. 

2 5 - 

Tetrahedrite. 

! 3 - 

Lionite. 

26. 

Wehrlite. 



SILVER. 


LIST 

OF THE PRINCIPAL SILVER 

MINERALS FOUND 


THE UNITED STATES. 


NAME. 

1. Alaskaite (sulphide of bis¬ 
muth, silver and lead). 

2. Argentite (sulphuret or sul¬ 
phide of silver, vitreous silver, 
silver glance). 

3. Bromyrite (bromide of silver, 
bromic silver). 


COMPOSITION. 

Silver, bismuth, 
lead, copper, sul¬ 
phur. 

Silver, sulphur. 


Silver, bromine. 



APPENDIX. 


4. Cerargyrite (muriate or chlo- 

• - 

ride of silver, horn-silver) 

5. Dyscrasite (antimonial sil¬ 
ver). 

6. Electrum (argentiferous 
gold). 

7. Embolite (chloro-bromide of 
silver). 

8. Freieslebenite (antimonial 
sulphide of silver and lead). 

9. Hessite (telluride of silver, 
telluric silver). 

10. Iodyrite (iodide of silver, 
iodic silver). 

11. Miargyrite (sulphide or sul- 
phuret of silver and antimony) 

12. Native silver (free, wire, leaf, 
dendritic, etc.). 

13. Petzite (telluride of silver and 
gold). 

14. Polybasite (sulphide of silver, 
antimony and arsenic). 

15. Proustite(arsenicalsilverore, 
light red silver ore, ruby sil¬ 
ver). 


463 

Silver, chlorine. 

Silver, antimony. 

Silver, gold. 

Silver, chlorine, 
bromine. 

Silver, lead, anti¬ 
mony, sulphur. 

Silver, tellurium. 

Silver, iodine. 

Silver, antimony, 
sulphur. 

Silver. 

Silver, gold, tellu¬ 
rium. , 

Silver, antimony, 
arsenic, copper, 
sulphur. 

Silver, arsenic, sul¬ 
phur. 



464 


MANUAL OF ASSAYING. 


16. Pyrargyrite (antimonial red 
silver ore, dark red silver ore, 
ruby silver). 

17. Schapbachite (bismuth-sil¬ 
ver, sulphide of bismuth, sil¬ 
ver and lead). 

18. Schirmerite (same as above 
but proportions varying). 

19. Stephanite (sulphide of silver 
and antimony, brittle silver, 
black silver). 

20. Sternbergite (sulphide of sil¬ 
ver and iron). 

21. Stetefeldite (oxide of anti¬ 
mony with silver, etc.). 

22. Stromeyerite(sulphideorsul- 
phuret of silver and copper, 
silver-copper glance). 

,23. Sylvanite (graphic tellurium, 
yellow tellurium, telluride of 
silver and gold). 

24. Tetrahedrite (gray copper 
ore, sulphide of copper, anti¬ 
mony, silver, etc.). 


Silver, antimony, 
sulphur. 

Silver, bismuth, 
lead, sulphur. 

Silver, bismuth, 
lead, sulphur. 

Silver, antimony, 
sulphur. 

Silver, iron, sul¬ 
phur. 

Silver, antimony, 
copper, oxygen, 
sulphur. 

Silver, copper, sul¬ 
phur. 

Silver, gold, tellu¬ 
rium (antimony). 

Silver, copper, an¬ 
timony, sulphur 
(arsenic,bismuth, 
mercury, zinc, 
etc.) 



APPENDIX. 


465 


MINERALS LIKELY TO CARRY SILVER. 


I. 

Algodonite. 

22. 

Melaconite. 

2. 

Altaite. 

2 3 - 

Miillerite. 

3 - 

Arsenopyrite. 

24. 

Nagyagite. 

4 - 

Barnhardite. 

2 5 - 

Native antimony. 

5 * 

Bornite. 

26 

“ arsenic. 

6. 

Boulangerite. 

27. 

“ bismuth. 

7 - 

Calaverite. 

28. 

“ copper. 

8. 

Cerussite. 

29. 

“ gold. 

9 - 

Chalcopyrite. 

3 °- 

11 mercury. 

10. 

Coloradoite. 

3 1 - 

“ tellurium. 

11. 

Enargite. 

3 2 - 

Petzite. 

12. 

Ferro-tellurite. 

33 - 

Pyrite. 

13* 

Galenite. 

34 - 

Realgar. 

14. 

Geocronite. 

35 - 

Smaltite. 

15 - 

Gold amalgam. 

3 6 - 

Sphalerite. 

16. 

Henryite. 

37 - 

Sylvanite. 

17. 

Hessite. 

38 . 

Tellurite. 

18. 

Joseite. 

39 - 

Tellurpyrite. 

19. 

Leucopyrites. 

4 °. 

Tetradymite. 

20. 

Lionite. 

41. 

Wehrlite. 

21. 

Magnolite. 





466 


MANUAL OF ASSAYING. 


COPPER. 


LIST OF THE PRINCIPAL COPPER MINERALS FOUND IN 

THE UNITED STATES. 


NAME. 

1. Aikinite (needle ore, acicular 
bismuth, cupreous bismuth). 

2. Algodonite (arsenide of cop- 
Per). 

3. Atacamite (muriate of cop¬ 
per, oxy-chloride of copper). 

4. Aurichalcite (carbonate of 
zinc and copper). 

5. Azurite (mountain blue, blue 
carbonate of copper, blue 
malachite, azure copper ore). 

6. Barnhardite (sulphide of iron 
and copper). 

7. Bornite (purple copper ore, 
variegated copper ore, erubes- 
cite , sulphide of copper and 
iron,horseflesh ore). 

8. Bournonite (triple sulphuret 
of copper, lead and antimony). 

9. Brochantite (sulphate of cop- 
P er )- 


COMPOSITION. 

Copper, bismuth, 
lead, sulphur. 

Copper, arsenic. 

Copper, chlorine, 
oxygen (water). 

Copper, zinc, car¬ 
bon, oxygen 
(water). 

Copper, carbon, 
oxygen (water). 

Copper, iron, sul¬ 
phur. 

Copper, iron, sul¬ 
phur. 


Copper, lead, anti¬ 
mony, sulphur. 
Copper, oxygen, 
sulphur (water). 



APPENDTX. 


46 7 


10. Caledonite (cupreous sul- 
phato-carbonate of lead). 

11. Carrollite (sulphide of cobalt 
(nickel) and copper). 

12. Chalcanthite (blue vitriol, 
copper vitriol, sulphate of 
copper). 

13. Chalcocite (copper glance, 
vitreous copper, sulphuret or 
sulphide of copper). 

14. Chalcopyrite (copper pyrites, 
pyritous copper, sulphide of 
copper and iron). 

15. Chrysocolla(mountain green, 
mountain blue, silicate of cop- 
per). 

16. Covellite (indigocopper, blue 
copper, sulphide of copper). 

17. Cuprite (red oxide of copper, 
cupreous oxide, tile ore). 

18. Domeykite (arsenical copper,- 
arsenide of copper). 

19. Enargite (sulph-arsenite of 
copper). 

20. Harrisite(sulphide of copper) 


Copper, lead, car¬ 
bon, oxygen, sul¬ 
phur. 

Copper, cobalt 
(nickel), sulphur. 

Copper, oxygen, 
sulphur (water). 

Copper, sulphur. 


Copper, iron, sul¬ 
phur. 

Copper, silicon, ox¬ 
ygen (water). 

Copper, sulphur. 

Copper, oxygen. 

Copper, arsenic. 

Copper, arsenic,sul¬ 
phur. 

Copper, sulphur. 



468 


MANUAL OF ASSAYING. 


21. Malachite (mountain green, 
green carbonate of copper, 
green malachite,greencopper). 

22. Melaconite (black oxide of 
copper, black copper, cupric 
oxide). 

23. Native copper (sometimes 
with silver). 

24. Pseudomalachite (phosphate 
of copper). 

25. Stromeyerite (sulphuret of 
silver and copper, silver-cop¬ 
per glance). 

26. Tennantite (sulph-arsenite of 
copper). 

27. Tetrahedrite (gray copper 
ore, sulphide of copper and 
antimony with various other 
sulphides). 

28. Torbernite (copper-uranite, 
phosphate of uranium and 
copper). 

29. Uranochalcite (oxide of uran¬ 
ium with oxide of copper and 
sulphate of lime) 


Copper, carbon, ox¬ 
ygen (water). 

Copper, oxygen. 


Copper (silver). 

Copper, oxygen, 
phosphorus 
(water). 

Copper, silver, sul¬ 
phur. 

Copper, arsenic, 
sulphur (iron). 

Copper, antimony, 
sulphur (arsenic, 
bismuth, silver, 
mercury, zinc,etc) 

Copper, uranium, 
phosphorus, ox¬ 
ygen (water). 

Copper, uranium, 
oxygen, sulphur, 
calcium (water). 



APPENDIX. 


469 


30. Vauquelinite (chromate of Copper, lead, chro- 

copper and lead). mium, oxygen. 

31. Whitneyite (arsenide of cop- Copper, arsenic. 

P er )- 

LEAD. 


LIST OF THE PRINCIPAL LEAD MINERALS FOUND IN THE 

UNITED STATES. 


NAME. 

1. Alaskaite (sulphide of bis¬ 
muth, silver and lead). 

2. Altaite (telluride of lead). 

3. Anglesite (lead-vitriol, sul¬ 
phate of lead). 

4. Boulangerite (sulphide of 
lead and antimony). 

5 Bournonite (triple sulphuret 
of copper, lead and antimony). 

6. Caledonite (cupreous-su 1 - 
phato-carbonate of lead). 

7. Cerussite (white lead ore, 
carbonate of lead). 

8. Dechenite (vanadate of lead 
and zinc). 

9. Descloizite (vanadate of 
lead). 


COMPOSITION. 

Lead, bismuth, sil¬ 
ver, copper, sul¬ 
phur. 

Lead, tellurium. 

Lead, oxygen, sul¬ 
phur. 

Lead, antimony, 
sulphur. 

Lead, copper, anti¬ 
mony, sulphur. 

Lead, carbon, cop¬ 
per, oxygen, sul- * 
phur. 

Lead, carbon, oxy¬ 
gen. 

Lead, vanadium, 
zinc, oxygen. 

Lead, vanadium, 
oxygen. 





470 


MANUAL OF ASSA YING. 


10. Freieslebenite (antimonial 
sulphide of silver and lead). 

11. Galenite (galena, sulphide or 
sulphuret of lead). 

12. Geocronite (sulph-arseno-an- 
timonite of lead). 

13. Henryite (telluride of lead, 
with a little iron). 

14. Jamesonite (sulph-antimon- 
ite of lead). 

15. Kobellite (sulphide of lead, 
bismuth and antimony). 

16. Lanarkite (sulphato-carbon- 
ate of lead). 

17. Leadhillite (sulphato-tri-car- 
bonate of lead). 

18. Massicot (plumbic ochre, 
yellow oxide of lead). 

19. Mimetite (green lead ore, 
arsenate of lead). 

20. Minium (red oxide of lead). 

21. Miillerite (telluride of gold, 
silver and lead). 


Lead, silver, anti¬ 
mony, sulphur. 

Lead, sulphur. 

Lead, antimony, 
arsenic, sulphur. 

Lead, tellurium, 
iron. 

Lead, antimony, 
sulphur (iron). 

Lead, bismuth, an¬ 
timony, sulphur. 

Lead, carbon, oxy¬ 
gen, sulphur. 

Lead, carbon, oxy¬ 
gen, sulphur. 

Lead, 1 part; oxy¬ 
gen, 1 part. 

Lead, arsenic, oxy¬ 
gen (chlorine, 
phosphorus). 

Lead, 3 parts; oxy¬ 
gen, 4 parts. 

Lead, gold, silver, 
tellurium. 



APPENDIX. 


47 * 


22. Nagyagite (black tellurium, 
foliated tellurium, telluride of 
gold and lead). 

23. Native lead. 

24. Plumbogummite (phosphate 
of alumina and lead). 

25. Pyromorphite (phosphate 
and chloride of lead). 

26. Schapbachite (bismuth-sil¬ 
ver, sulphide of bismuth, sil¬ 
ver and lead). 

27. Schirmerite (same as above 
but proportions varying). 

28. Stolzite (tungstate of lead). 

29. Vauquelinite (chromate of 
copper and lead). 

30. Wulfenite (yellow lead ore, 
yellow lead-spar, molybdate 
of lead). 


Lead, gold, tellu¬ 
rium (antimony, 
sulphur). 

Lead. 

Lead, aluminum, 
oxygen, phos¬ 
phorus. 

Lead, phosphorus, 
oxygen, chlorine. 

Lead, bismuth, sil¬ 
ver, sulphur. 

Lead, bismuth, sil¬ 
ver, sulphur. 

Lead, tungsten, ox¬ 
ygen. 

Lead, copper, chro¬ 
mium, oxygen. 

Lead,molybdenum, 
oxygen. 


Note .—For descriptions of the above, and of other American 
and foreign minerals of gold, silver, copper and lead, consult 
Dana’s System of Mineralogy, 5th Ed. with Sup., and Prof. J. 
Alden Smith’s Report as State Geologist of Colorado, for 1880. 



47 2 


MANUAL OF ASSAYING. 


LIST OF USEFUL BOOKS ON SUBJECTS MORE OR LESS 
CONNECTED WITH ASSAYING. 

General Sciefice. 

Johnson s New Universal Cyclopaedia. 4 vols. Vols. 1 
and 2, 1876; vol. 3, 1877; vol. 4, 1878. New York. 

General Chemistry. 

Watts, H.: A Dictionary of Chemistry. 10 vols. Vols. 
1-6, 1868; 1st sup., 1872; 2d sup. (vol. 7), 1875; 3d 
sup. (vol. 8), Part I, 1879; Part II, 1881. London. 

Chemical Technology. 

Wagner, R.: A Hand-book of Chemical Technology. 
Translated from 8th German edition by William 
Crookes. New York, 1872. 

Reference Books on Chemistry. 

Roscoe, H. E., and C. Schorlemmer: A Treatise on Chem¬ 
istry. 2 vols. Vol. 1, The Non-Metallic Elements, 
1878; vol. 2, Metals, Parts I and II, 1879. New 
York. 

Miller, W. A.: Elements of Chemistry, Theoretical 
and Practical. 3 vols. 6th edition. London, 
1877-1880. 

Text-books on Theoretical Che?nistry. 

Barker, Geo. F.: A Text-book of Elementary Chemis¬ 
try, Theoretical and Inorganic. Louisville. 




APPENDIX. 


473 


Roscoe H. E. : Lessons in Elementary Chemistry, In¬ 
organic and Organic. New edition. London, 1880. 

General Qualitative Analysis. 

Fresenius, C. R.: Manual of Qualitative Chemical Anal¬ 
ysis. 9th English edition. London, 1876. 

Douglas , A. H., and A. B. Prescott: Qualitative Chem¬ 
ical Analysis. 3d edition. New York, 1880. 

Eliot, C. W., and F. H. Storer: A Compendious Man¬ 
ual of Qualitative Chemical Analysis. New York, 

1879. 

General Qua?ititative Analysis. 

Fresenius , C. R.: Manual of Quantitative Chemical 
Analysis. 7th English edition. London, 1876. 
Classen, A.: Elementary Quantitative Analysis. Trans¬ 
lated by E. F. Smith. Phila., 1878. 

Cairns, F. A.: A Manual of Quantitative Chemical 
Analysis for the Use of Students. New York, 

1880. 

Special Quantitative Analysis. 

Rammelsberg, C.: Guide to a Course of Quantitative 
Chemical Analysis, especially of Alloys, Minerals 
and Furnace Products. Translated by J. Towler. 
New York, 1872. 

Wohler, F.: Hand-book of Mineral Analysis. Phila., 
1870. 



474 


MANUAL OF ASSAYING. 


Volumetric Analysis. 

Sutton, F.: A Systematic Hand-book of Volumetric 
Analysis. 4th edition. London, 1882. 

Hart, Edward: A Hand-book of Volumetric Analysis. 

New York, 1878. 

Laboratory Manipulation. 

Mor jit (Campbell and Clarence ) .• Chemical and Phar¬ 
maceutical Manipulations. Phila., 1857. 

Williams, C. G.: A Hand-book of Chemical Manipula¬ 
tion. London, 1857; supplement, 1879. 

Geology. 

Cotta, Bernh. v. Treatise on Ore Deposits. Translated 
from 2d German edition by F. Prime, and revised 
by author. New York, 1870. 

Dana, J. D.: A Text-book of Geology. 2d edition. 
New York, 1874. 

Dana, J. D.: Manual of Geology. New York, 1881. 

Le Conte, Joseph : Elements of Geology. A text-book 
for colleges and for the general reader. New York, 
1878. 

Rutley, C. L.: The Study of Rocks. 2d edition. New 
York, 1880. 

ALineralogy. 

Dana, J. D.: A System of Mineralogy. 5th edition, 
1868; Appendix I, 1872; Appendix II, 1875; Ap¬ 
pendix III, 1882. New York. 



APPENDIX. 


475 


Dana, J. D.: Manual of Mineralogy and Lithology. 

3d edition. New York, 1878. 

Brush , G. J.: Manual of Determinative Mineralogy, 
with an Introduction on “ Blow-pipe Analysis.” 
New York, 1878. 

Foye, J. C.: Tables for the Determination, Description, 
and Classification of Minerals. Chicago, 1882. 
Frazer, P.: Tables for the Determination of Minerals. 
Phila., 1874. 

Hanks , H. G.: Fourth Annual Report of the State 
Mineralogist of California. Sacramento, 1884. 

Blo w -pipe A ?ialysis. 

Planner's Manual of Qualitative and Quantitative Anal- 
ysis with the Blow-pipe. Translated by H. B. 
Cornwall. 4th edition. Revised and corrected. 
New York, 1880. 

Cornwall, H. B.: Manual of Blow-pipe Analysis, Qual¬ 
itative and Quantitative. With a Complete Sys¬ 
tem of Determinative Mineralogy. NewYork, 1882. 
Atwood, Geo: Practical Blow-pipe Assaying. New 
York, 1881. 

Plympton, G. W.: The Blow-pipe. A Guide to its Use 
in the Determination of Salts and Minerals. New 
York, 1874. 

Elderhorst, W?n.: Manual of Qualitative Blow-pipe 
Analysis. Revised by H. B. Nason. Phila., 1881. 




476 


MANUAL OF ASSAYING. 


Ross, W. A.: The Blow-pipe in Chemistry, Mineralogy, 
and Geology London, 1884. 

Ross, W. A.: Pyrology,or Fire Chemistry. London, 1875. 

Metallurgy a?id Mining. 

Kerl, Prof.: Practical Treatise on Metallurgy. Trans¬ 
lated by Wm. Crookes and E. Rohrig. Vol. 1, 
Lead, Silver, Zinc, etc., 1868; Vol. 2, Copper and 
Iron, 1869; Vol. 3, Steel, Fuel, and Supplement, 
1870. London. 

Lock , A. G.: Gold; Its Occurrence and Extraction. 
London and New York, 1882. 

Percy, John: Metallurgy. The Art of Extracting Met¬ 
als from their Ores. Part I, Silver and Gold. 
London, 1880. 

Percy, John: The Metallurgy of Lead. London, 1870. 

Percy, John: The Metallurgy of Fuel, Wood, Peat, 
Coal, Charcoal, Fire-clays. Revised edition. 

Callon, J.: Lectures on Mining. 3 vols. London and 
Paris. 1876-81. 

La?nborn, R. H.: Metallurgy of Copper. 6th edition. 
London, 1875. 

Lamborn, R. H.: Metallurgy of Silver and Lead 6th 
edition. London, 1878. 

Kustel, G.: Roasting of Gold and Silver Ores, and the 
Extraction of their Respective Metals without 
Quicksilver. New edition (2d). San Francisco, 
1880. 



APPENDIX. 47J7 

Makin , £. //..• A Manual of Metallurgy. 2d edition. 
London, 1873. 

Collms , J. H.: A First Book of Mining and Quarrying. 
London, 1872. 

Bowie, Aug. J ’., Jr.: A Practical Treatise on Hydraulic 
Mining in California. New York, 1885. 

Davies , D. C.: A Treatise on Metalliferous Minerals 
and Mining. 2d edition. London, 1881. 

Davies , C: A Treatise on Earthy and other Min¬ 

erals and Mining. London, 1884. 

Egleston , 7 U Metallurgy of Gold, Silver, and Mercury 
in the United States. London and New York, 
1886. 

Phillips , y. A.: Mining and Metallurgy of Gold and 
Silver, London, 1867. 

Phillips , J. A.: A Treatise on Ore Deposits. London, 
1884. 

Phillips , J. A.: Elements of Metallurgy. London, 1874. 
Pomeroy , AT. A..* Mining Manual for Prospectors, Min¬ 
ers, and Schools. 3d edition. St. Louis, 1881. 
Kunhardt , fU. A?..- The Practice of Ore Dressing in 
Europe. New York, 1884. 

Randall , /*. M.: The Quartz Operator’s Hand Book. 

Revised and enlarged. New York, 1871. 

Van IVagenen , T. F.: Manual of Hydraulic Mining. 
For the Use of the Practical Miner. New York, 


1880. 



478 


MANUAL OF ASSAYING. 


Assaying. 

Aaron, C. H.: Assaying. In Three Parts. Part I, 
Gold and Silver Ores, 1884; Parts II and III, Gold 
and Silver Bullion, Lead, Copper, etc., 1885. San 
Francisco. 

Balling , C. A. M Die Probirkunde des Eisens und der 
Brennmaterialen. Prag, 1868. 

Balling , C. A. M.: Die Probirkunde. Anleitung zur 
Vornahme docimastischer untersuchungen der 
Berg-und Hiitten producte. Braunschweig, 1879. 

Bodeman , 77 /., and Bruno Kerl: Anleitung zur Berg- 
und Hiittenmannischen Probirkunde. 2d edition. 
Clausthal, 1857. 

Bodeman , Th ., and Bruno Kerl: A Treatise on the 
Assaying of Lead, Copper, Silver, Gold and Mer¬ 
cury. Translated by W. A. Goodyear. New York, 
1865. 

Chapman, E. Practical Instructions for the Deter¬ 
mination by Furnace Assay of Gold and Silver in 
Rocks and Ores. Toronto, Can., 1881. 

Kerl. Bruno : Metallurgische Probirkunst. 2d edition. 
Leipsig, 1882. 

Kerl , Bruno: The Assayer’s Manual. Translated by 
William T. Brannt, edited by William H. Wahl. 
Philadelphia and London, 1883. 

Lieber , 0 . M.: The Assayer’s Guide. Phila., 1852. 



APPENDIX. 


479 


Mitchell, John: A Manual of Practical Assaying. 
Edited by Wm. Crookes. 6th edition. New York, 
1888. 

North, Oliver: The Practical Assaver. London, 1874. 
Overman, F.: Practical Mineralogy, Assaying, and 
Mining. Phila., 1851. 

Phillips, J. S.: The Explorers’ and Assayers’ Compan¬ 
ion. San Francisco, 1879. 

Ricketts , P. de P.: Notes on Assaying and Assaying 
Schemes. New York, 1879. 

Silversmith, J.: A Practical Hand-Book for Miners, 
Metallurgists, and Assayers. New York, 1866. 
Triplett, Frank: How to Assay. St. Louis, 1881*. 

Metric System ; Weights and Measures. 

Barnard, F. A. P.: The Metric System of Weights and 
Measures. 2d edition. New York, 1872. 

Egleston, T.: Tables of Weights, Measures, Coins, etc. 
New York, 1871. 

Oldberg, O.: Weights, Measures, and Specific Gravity. 
Chicago, 1885. 

Mining Law. 

Copp, H. N.: American Mining Code. 3d edition. 
1880. 

* Besides the above, there have been a number of publications 
from 1741 to about 1850 which are either obsolete jn their teach¬ 
ings. or the information contained therein is embraced in the 
preceding. 



480 


MANUAL OF ASS A YING. 


Carpe?iter , AT. B.: Mining Code. 3d edition. 1880. 
Wade , W. P.: Manual of Mining Law. St. Louis, 
1882. 

Wilson , C. S.: Mining Laws of the United States, Col- 
• * 

orado, New Mexico, and Arizona. 1881. 

It is not pretended that the above list is complete, 
nor even that it comprises all the best works; it is 
simply a list of some that are considered standard 
authorities in their respective lines, save perhaps in 
the department of assaying, where certain ones are 
included that are not particularly valuable. 

The plan of an assay laboratory, given on the op¬ 
posite page, shows a simple and convenient arrange¬ 
ment, which can be adapted to almost any room. 




APPENDIX . 




























































482 


MANUAL OF AS SAVING. 


FORM FOR CERTIFICATE OF ASSAY. 

Almost every assayer has his own particular blank, 
but so long as the certificate states plainly the results 
of his work, any little differences of detail are un¬ 
important. The form given below is about as satis¬ 
factory as any. 





































APPENDIX. 


483 


ASSAYER’S OUTFIT. 


With the following outfit the assayer can 
perform the ordinary crucible and scorification 
assays of gold, silver, copper and lead ores: 


Hammers, sledge, medium and small, 

• 

$ 2 

00 

Iron mortar (8 in. diam., 1 gal.) and pestle, 


1 

5° 

Plate and Rubber, ..... 

• 

10 

00 

Steel spatulas, one large and one small, 



75 

Sieves, 20, 40 and 100 mesh, brass frames, 

• 

3 

5° 

Ore or pulp scales, . 


22 

00 

Assay balance, with weights (1 grm down 

to 



tV mgrm),. 

• 

73 5° 

Set gramme weights, 100 grms down, . 


6 

00 

Set assay ton weights, .... 

• 

6 

00 

Furnace, Brown’s portable, new form, 


20 

00 

6 muffles, size J, 12x6x4 inches, 

• 

6 

00 

1 pair crucible tongs, . . . . . 


1 

2 5 

1 pair scorifier tongs, .... 

• 

1 

00 

1 pair cupel tongs, . . . . . 


1 

00 

Shovel, scraper and hoe, .... 

• 

1 

00 

Scorification mould, . . . . . 


1 

00 

Crucibles, 6 doz., 1 doz. covers, 

• 

4 75 

Scorifiers, 200 2^ inch, 200 3 inch, 


7 

20 

Cupels, 6 doz. 1 y x inch, .... 

• 

3 

00 

Cupel mould, 1 y inch, brass, 


2 

5° 



4 8 4 


MANUAL OF ASSAYING. 


Piece rubber cloth, 

. . $ 1 

OO 

Alcohol lamp, .... 

• • 

5 ° 

Ring stand, ..... 

• • 

75 

Wire triangle, .... 

• • 

10 

i doz. i inch porcelain crucibles, 

. . 1 

44 

i doz. i y inch porcelain crucibles, 

. . 2 

16 

i quart wash-bottle, 

• • 

75 

i pair 3 inch watch-glasses, 

• • 

3 ° 

Blow-pipe, ..... 

• • 

20 

Magnifying glass, pocket size, 

. . 1 

OO 

Magnet, ..... 

• • 

20 

Small steel hammer and anvil, 

1 

OO 

Pair steel pincers, .... 

• • 

2 5 

Small cold chisel, 

• • 

35 

Horn spoon, ..... 

• • 

2 5 

i button brush .... 

• • 

5 ° 

6 parting flasks, . . . * 

. . 1 

20 

6 annealing cups, 

• • 

60 

24 sample bottles and corks, 

• • 

75 

12 test-tubes, assorted, 

• • 

35 

1 box gummed labels, 

• • 

15 

1 lb. bottle pure nitric acid, 

• • 

40 

2 lbs. bi-carbonate soda, 

• • 

20 

1 lb. carbonate of potash, in bottle, 

• • 

3 ° 

y lb. cyanide of potash, in bottle, . 

• • 

2 5 

y lb. borax glass, 

• 

• • 

2 5 







APPENDIX. 


485 


2 lbs. flour, 

1 lb. argol, . 

2 lbs. nitre (nitrate potash), 
2 lbs. litharge, 

1 lb. charcoal, pulverized, 

1 lb. silica, 
y 2 lb. sheet lead, 

1 lb. granulated lead, 

2 lbs. bone-ash, 

y 2 oz. pure silver foil, 


. $ 20 

*5 

3° 

2 5 

2 5 

10 

. 20 

2 5 

3° 

75 


Total,.$191 90 


BLOW-PIPE OUTFIT. 

ApfaraDis for B low-fiping , according to Prof. 
Plattner, the whole in elegant velvet-lined, polished 
mahogany case, with handle and lock, for travelling, 


complete, with case, $38. 

1 set of three porcelain 
dishes. 

1 diamond steel mortar. 

1 pair platinum pointed 
forceps. 

1 pair heavy tip steel for¬ 
ceps. 

1 pair steel forceps. 

I steel chisel. 


The set includes: 

1 charcoal borer, 4 cor¬ 
nered, with spatula. 

1 charcoal borer, club 
shape. 

1 pair fine scissors. 

1 wire holder, with 3 plat¬ 
inum wires in the han¬ 
dle. 

1 Plattner’s blow-pipe. 





486 


MANUAL OF ASS A YlNG. 


lamp, with patent swivel, 
nickel-plated, 
i charcoal saw. 
i holder for the mat¬ 
rasses. 

i nickel-plated Plattner’s 
blow-pipe. 

i heavy platinum tip for 
same. 

i steel hammer with wire 
handle. 

i set mould and stamps, 
i pair of steel nippers, 
Plattner’s. 
i double lens, 
i knife, ivory handle, 
i dropping pipette, 
i camel’s hair brush. 

6 matrasses. 

i alcohol lamp, with nick¬ 
el-plated air-tight top. 
i chamois skin. 

6 glass tubes. 

6 pieces square-cut char¬ 
coal. 


Metal trays for coal, ashes, 
and filters. 

18 flat-top, stoppered and 
labelled re-agent bot¬ 
tles, containing the fol¬ 
lowing re-agents: 

Test lead. 

Tin. 

Phosphorus salt. 

Borax powder. 

Borax glass. 

Boracic acid, fused. 
Boracic acid, crvst. 
Plattner’s flux. 

Bismuth flux. 

Carbonate soda. 

Potash oxalate. 

Salt. 

Soda nitrate. 

Charcoal. 

Boneash, sieved. 

Boneash, washed. 

Copper oxide. 

Bi-sulphate potash. 

Test papers. 






SECTION III. 


TABLES. 

MULTIPLICATION TABLE FOR GOLD AND SILVER. 


SILVER. 

GOLD. 

OUNCES. 

VALUE. 

OUNCES. 

VALUE. 

T. 

Si 20 

I. 

$20 67 


S v x J 


2 . 

2 58 

2. 

4i 34 



7. 

7 87 


62 OI 

J 





s 16 

4 . 

82 68 

r. 

J 

6 45 

c. 

io 3 35 

j. 


6. 

7 74 

6. 

124 02 




7 .... 

Q O'? 

7 . 

144 69 

/. 



8. .... 

IO X2 

8 . 

16s x6 

n . 

II 6 l 

0 . 

J O 

186 03 

y . 


7 ' 


Note —The above table is more relative than actual. $20.00 is commonly 
used as a factor for gold, and for silver the value per ounce fluctuates with 
the market. 


487 



































488 


MANUAL OF ASSA Y1NG. 


TABLE OF VALUES OF GOLD AND SILVER. 


I 

I 


I 


I 


I 


I 


I 


» 

WEIGHT. 

Of Gold is 

worth 

Of Silver is 

worth 

grain Troy. 

$0.0430 

$0.0026 

pennyweight Troy =24 
grains Troy. 

1-0335 

0.0646 

ounce Troy =20 penny¬ 
weights Troy = 480 grains 
Troy. 

20.67 18 

I.2929 

ounce Avoirdupois = 437^ 
grains Troy. 

18.8415 

1.1784 

pound Troy= 12 ounces Troy 
= 240 pennyweights Troy = 
5,760 grains Troy. 

248.0620 

1 5-5 *5 1 

pound Avoirdupois = 16 
ounces Avoirdupois = 7,000 
grains Troy. 

301.4642 

18.855I 

ton Avoir. = 2,000 pounds 

Avoir _ ' 29,166 ounces Troy (_ 

* ) 32,000 ounces Avoir, i 

14,000,000 grains Troy. 

602,928.4660 

37 , 710.3846 


Note.— The above values are figured on the basis of $20.67 per 
Troy oz. for gold, and $1.29 for silver. Were the factors made $20 
for gold, and the fluctuation prices of the market for silver, the 
values given would be varied considerably. 




















APPENDIX . 


489 


TABLES OF WEIGHTS. 

AVOIRDUPOIS WEIGHT. 

16 Drams—i Ounce. 

16 Ounces^ 1 Pound. 

28 Pounds= 1 Ouarter.* 

4Quarters=i Hundredweight. 

20 Hundred weights 1 Ton of 2240 pounds. 

AVOIRDUPOIS WEIGHT. 

i dram. 

1 ounce= 16 drams. 

1 pound= 16 ounces= 256 drams. 

1 quarter=28 pounds = 448 ounces=7i68 drams. 

1 h’dwt = 4 quarters^ 112 pounds^ 1792 ounces=28672 
drams 

1 ton = 2o h’dvvt = 8o quarters = 2240 pounds=35840 
ounces = 57344o drams. 

AVOIRDUPOIS WEIGHT. 

25 Pounds=i Ouarter. 

4 Quarters=i Hundredweight. 

20 Hundred weight=i Ton of 2000 pounds. 

AVOIRDUPOIS WEIGHT. 

i quarter=25 pounds = 40o ounces = 64oo drams. 


* In some parts of the United States. 



490 


MANUAL OF A SSA YlNG. 


i h’dwt=:4 quarters — ioo pounds =1600 ounces = 
25600 drams. 

1 ton = 2o h dwt=8o quarters = 2000 pounds = 32000 
ounces—512000 drams. 

TROY WEIGHT. 

24 Grains=i Pennyweight. 

20 Penny weights = 1 Ounce. 

12 Ounces^ 1 Pound. 

TROY WEIGHT. 

i grain. 

1 pennyweight^ 24 grains. 

1 ounce=2o pennyweights = 48o grains. 

1 pound=i2 ounces = 24o pennyweights = 576o grains. 

apothecaries’ weight. 

20 Grains=i Scruple. 

3 Scruples=i Dram. 

8 Drams = 1 Ounce. 

12 Ounces=i Pound. 

apothecaries’ weight. 

1 grain. . 

1 scruple = 2o grains. 

1 dram = 3 scruples = 6o grains. 

1 ounce = 8 drams = 24 scruples = 48o grains. 

1 pounds 12 ounces=96 drams= 288 scruples = 576o 
grains. 



APPENDIX. 


i pound, Troy, 
i pound, Apothecaries’, 
i pound, Avoirdupois, 


491 


— 576° grains. 

— 576° grains. 

= 7000 Troy grains. 


FRENCH OR METRIC SYSTEM OF WEIGHTS. 


i Milligramme = 
1 Centigramme = 
1 Decigramme = 
1 Gramme = 
1 Decagramme = 
1 Hectogram me= 
1 Kilogramme = 
1 Myriagramme = 

10 Milligrammes (mgrs) 
10 Centigrammes 
10 Decigrammes 
10 Grammes 
10 Decagrammes 
10 Hectogrammes 
10 Kilogrammes 


.001 of a Gramme. 

.01 “ “ 

J u u 

i Gramme. 

10 Grammes. 

100 “ 

1000 “ 

10000 “ 

or 

l = i Centigramme (cgr). 

= 1 Decigramme (dgr). 

= 1 Gramme (grm). 

= 1 Decagramme (dkgr). 
= 1 Hectogramme (hgr). 
= 1 Kilogramme (kgr). 

= 1 Myriagramme(myrgr) 


1 m g r - 

1 cgr. = 10 mgrs. 

1 dgr. = 10 cgrs. = 100 mgrs. 

1 grm. = 10 dgrs.= ioo cgrs.= 1,000 mgrs. 

1 dkgr.= 10 grms.= 100 dgrs.= 1,000 cgrs.= 
mgrs. 


10,000 



492 


MANUAL OF ASSA YING. 


i hgr.= io dkgrs.= ioo grms. = 1,000 dgrs.= 10,000 
cgrs.—100,000 mgrs. 

1 kgr.= 10 hgrs.= 100 dkgrs.= 1,000 grms.= 10,000 
dgrs. = 100,000 cgrs. = 1,000,000 mgrs. 

1 myrgr.= io kgrs.= ioo hgrs.= 1,000 dkgrs. = 10,000 
grms. = 100,000 dgrs. = 1,000,000 cgrs. = 10,000,000 
mgrs. 

1 gramme= 15.43235 Troy grains. 



APPENDIX. 


493 


EQUIVALENTS OF SOME OF THE ENGLISH AND FRENCH 

WEIGHTS.* 


Troy Grains. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Grammes. 

1 

2 

3 

4 

5 

6 

7 

8 

9 


Grammes. 
.064798 
.129597 
.194396 
•259195 
•323994 
3^793 
•453592 
-5 1 839 1 

•58319° 

Troy Grains. 

I5-43235 
30.86470 
46.29705 
61.72940 
7 7. 1 6 1 75 
92.59410 
108.02645 
123.45880 
138.89115 


* T. Egleston’s Tables of Weights, Measures, Coins, etc., p. 24. 



494 


MANUAL OF ASS A YING. 


ASSAY TON EQUIVALENTS IN GRAMMES, TROY 

GRAINS, AND TROY OUNCES. 

Based on i gramme = i5.43235 Troy grains; hence 1 assay ton 
or 2g. 166 grammes = 15.43235 x 29.166=450.09992 Troy grains. 


Assay 

Tons. 

Value in 
Grammes. 

Value in 

Troy Grains. 

Value in 
Troy.Ounces. 

0.05 

1.458 

22.504 


0.10 

2.916 

45.009 


0.15 

4.374 

67.514 


0.20 

5.833 

90.019 


0.25 

7.291 

112.524 


0.30 

8.749 

135.029 


0.35 

10.208 

157.534 


0.40 

11.666 

180.039 


0.45 

13.124 

202.544 


0.50 

14.583 

225.049 


0.55 

16.041 

247.554 


0.60 

17.499 

270.059 


0.65 

18.958 

292.564 


0.70 

20.416 

315.069 


0.75 

21.874 

337.574 


0.80 

23.333 

360.079 


0.85 

24.791 

382.584 


0.90 

26.249 

405.089 


0.95 

27.708 

427.594 


1.00 

29.166 

450.099 
































APPENDIX. 


495 


ASSAY 


Assay- 

Tons. 


1.05 
1.10 
1.15 
1.20 
1.25 
1.30 
1.35 
1.40 
1.45 
1.50 
1.55 
1.60 
1.65 
1.70 
1.75 
1.80 
1.85 
1.90 
1.95 
2.00 


TON EQUIVALENTS-CONTINUED. 


% Value in 
Grammes. 


30.624 
32.083 
33.541 
34.999 
36.458 
37.916 
39.374 
40.833 
42.291 
43.749 
45.208 
46.666 
48.124 
49.583 
51\041 
52.499 
53.958 
55.416 
56.874 
58.333 


Value in 
Troy Grains. 


472.604 
495.109 
517.614 
540.119 
562.624 
585.129 
607.634 
630.139 
652.644 
675.149 
697.654 
720.159 
742.664 
765.169 
787.674 
810.179 
832.684 
855.189 
877.694 
900.199 


Value in 
Troy Ounces. 


1 .032 
1.078 
1.125 
1.173 
1.219 
1.266 
1.313 
1.360 
1.407 
1.453 
1.500 
1.547 
1.594 
1.641 
1.667 
1.735 
1.782 
1.829 
1.875 













496 


MANUAL OF ASS A YING. 


ASSAY 


Assay 

Tons. 


2.05 
2.10 
2.15 
2.20 
2.25 
2.30 
2.35 
2.40 
2.45 
2.50 
2.55 
2.60 
2.65 
2.70 
2.75 
2.80 
2.85 
2.90 
2.95 
3.00 


TON EQUIVALENTS-CONTINUED. 


Value in 
Grammes. 

Value in # 
Troy Grains. 

Value in 
Troy Ounces. 

59.791 

922.704 

1.922 

61.249 

945.209 

1.969 

62.708 

967.714 

2.016 

64.166 

990.219 

2.063 

65.624 

1012.724 

2.110 

67.083 

1035.229 

2.157 

68.541 

1057.734 

2.204 

69.999 

1080.239 

2.250 

71.458 

1102.744 

2.297 

72.916 

1125.249 

2.344 

74.374 

1147.754 • 

2.391 

75.833 

1170.259 

2.438 

77.291 

1192.764 

2.485 

78.749 

1215.269 

2.531 

80.208 

1237/774 

2.579 

81.666 

1260.279 

2.626 

83.124 

1282.784 

2.672 

84.583 

1305.289 

2.719 

86.041 

1327.794 

2.766 

87.499 

1350.299 

2.813 















05 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

95 

00 


AP PEND IX. 


497 


TON EQUIVALENTS-CONTINUED. 


Value in 
Grammes. 


88.958 
90.416 
91.874 
93.333 
94.791 
96.249 
97.708 
99.166 
100.624 
102.083 
103.541 
104.999 
106.458 
107.916 
109.374 
110.833 
112.291 
113.749 
115.208 
116.666 


Value in 
Troy Grains. 


1372.804 
1395.309 
1417.814 
1440.319 
1462.824 
1485.329 
1507.834 
1530.339 
1552.844 
1575.349 
1597.854 
1620.359 
1642.864 
1665.369 
1687.874 
1710.379 
1732.884 
1755.389 
1777.894 
1800.399 


Value in 
Troy Ounces. 


2 . 860 
2.905 
2.954 
3.001 
3.048 
3.094 
3.141 
3.188 
3.235 
3.282 
3.329 
3.376 
3 423 
3.470 
3.516 
3.563 
3.610 
3.657 
3.704 
3.751 












49^ 


MANUAL OF ASSAYING. 


ASSAY TON EQUIVALENTS-CONTINUED. 


Assay 

Tons. 

Value in 
Grammes. 

4 05 

118.124 

4.10 

119.583 

4.15 

121.041 

4.20 

122.499 

4.25 

123.958 

4.30 

125.416 

4.35 

126.874 

4.40 

128.333 

4.45 

129.791 

4.50 

131.249 

4.55 

132.708 

4.60 

134.166 

4.65 

135.624 

4.70 

137.083 

4.75 

138.541 

4.80 

139.999 

4.85 

141.458 

4.90 

142.916 

4.95 

144.374 

5.00 

145.833 


Value in 

Troy Grains. 

Value in 
Troy Ounces. 

1822.904 

3.798 

1845.409 

3.845 

1867.914 

3.891 

1890.419 

3.938 

1912.924 

3.985 

1935.429 

4.032 

1957.934 

4.079 

1980.439 

4.126 

2002.944 

4.173 

2025.449 

4.220 

2047.954 

4.267 

2070.459 

4.313 

2092.964 

4.360 

2115.469 

4.407 

2137.974 

4.454 

2160.479 

4.500 

2182.984 

4.548 

2205.489 

4.595 

2227.994 

4.642 

2250.499 

4.689 
















APPENDIX . 


499 


ASSAY 


Assay- 

Tons. 


5.05 
5.10 
5.15 
5.20 
5.25 
5.30 
5.35 
5.40 
5.45 
5.50 
5.55 
5.60 
5.65 
5.70 
5.75 
5.80 
5.85 
5.90 
5.95 
6.00 


TON EQUIVALENTS-CONTINUED. 


Value in 
Grammes. 


147.291 
148.749 
150.208 
151.666 
153.124 
154.583 
156.041 
157.499 
158.958 
160.416 
161.874 
163.333 
164.791 
166.249 
167.708 
169.166 
170.624 
172.083 
173.541 
174.999 


Value in 
Troy Grains. 


2273.004 
2295.509 
2318.014 
2340.519 
2363.024 
2385.529 
2408.034 
2430.539 
2453.044 
2475.549 
2498.054 
2520.559 
2543.064 
2565.569 
2588.074 

2610.579 
2633.084 
2655.589 
2678.094 

2700.579 


Value in 
Troy Ounces. 


4.735 
4.782 
4.829 
4.876 
4.923 
4.970 
5.017 
5.064 
5.111 
5.157 
5.204 
5.251 
5.298 
5.345 
5.392 
5.439 
5.486 
5.532 
5.579 
5.626 












500 


MANUAL OF ASS A YJNG. 


ASSAY TON EQUIVALENTS-CONTINUED. 


Assay 

Tons. 

Value in 
Grammes. 

Value in 

Troy Grains. 

Value in 
Troy Ounces. 

6.05 

176.458 

2723.084 

5.673 

6.10 

177.916 

2745.589 

5.720 

6.15 ' 

179.374 

2768.094 

5.767 

6.20 

180.833 

2790.599 

5.814 

6.25 

182.291 

2813.104 

5.861 

6.80 

183.749 

2835.609 

5.908 

6 .35 

185.208 

2858.114 

5.954 

6.40 

186.666 

2880.619 

6.001 

6.45 

188.124 

2903.124 

6.048 

6.50 

189.583 

2925.629 

6.095 

6 .55 

191.041 

2948.134 

6.142 

6.60 

192.499 

2970.639 

6.189 

6.65 

193.958 

2993.144 

6.236 

6.70 

195.416 

3015.649 

6.283 

6.75 - 

196.874 

3038.154 

6.329 

6.80 

198.333 

3060.659 

6.376 

6.85 

199.791 

3083.164 

6.423 

6.90 

201.249 

3105.669 

6.470 

6.95 

202.708 

3128.174 

6.517 

7.00 

204.166 

3150.679 

6.564 













APPENDIX. 


501 


ASSAY TON EQUIVALENTS-CONTINUED. 


Assay 

Tons. 

Value in 
Grammes. 

Value in 

Troy Grains. 

Value in 
Troy Ounces. 

7.05 

205.624 

3173.184 

6.611 

7.10 

207.083 

3195.689 

6.658 

7.15 

208.541 

3218.194 

6.705 

7.20 

209.999 

3240.699 

6.751 

7.25 

211.458 

3263.204 

6.798 

7.30 

212.916 

3285.709 

6.845 

7.35 

214.374 

3308.214 

6.892 

7.40 

215.833 

3330.719 

6.939 

7.45 

217.291 

3353.224 

6.986 

7.50 

218.749 

3375.729 

7.033 

7.55 

220.208 

3398.234 

7.080 

7.60 

221.666 

3420.739 

7.127 

7.65 

223.124 

3443.244 

7.173 

7.70 

224.583 

3465.749 

7.220 

7.75 

226.041 

3488.254 

7.267 

7.80 

227.499 

3510.759 

7.314 

7.85 

228.958 

3533.264 

7.361 

7.90 

230.416 

3555.769 

7.408 

7.95 

231.874 

3578.274 

7.455 

8.00 

233.333 

3600.779 

7.502 














5° 2 


MANUAL OF ASSA YING. 


ASSAY 


Assay 

Tons. 


8.05 
8.10 
8.15 
8.20 
8.25 
8.30 
8.35 
8.40 
8.45 
8.50 
8 .55 
8.60 
8.65 
8.70 
8.75 
8.80 
8.85 
8.90 
8 .95 
9.00 


TON EQUIVALENTS-CONTINUED. 


Value in 
Grammes. 


234.791 
236.249 
237.708 
239.166 
240.624 
242.083 
243.541 
244.999 
246.458 
247.916 
249.374 
250.833 
252.291 
253.749 
255.208 
256.666 
258.124 
259.583 
261.041 
262.449 


Value in 
Troy Grains. 


3623.284 
3645.789 
3668.294 
3690.799 
3713.304 
3735.809 
3758.314 
3780.819 
3803.324 
3825.829 
3848.334 
3870.839 
3893.344 
3915.849 
3938.354 
3960.859 
3983.364 
4005.869 
4028.374 
4050.879 


Value in 
Troy Ounces. 


7.549 
7.595 
7.642 
7.689 
7.736 
7.783 
7.830 
7.877 
7.924 
7.970 
8.017 
8.064 
8.111 
8.158 
8.205 
8.252 
8.299 
8.346 
8.392 
8.439 














05 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

95 


APPENDIX . 


503 


TON EQUIVALENTS-CONTINUED. 


Value in 
Grammes. 


263.958 
265.416 
266.874 
268.333 
269 . 79 L 
271.249 
272.708 
274.166 
275.624 
277.083 
278.541 
279.999 
281.458 
282.916 
284.374 
285.833 
287.291 
288.749 
290.208 
291.666 


Value in 
Troy Grains. 


4073.384 
4095 . 88 l > 
4118.394 
4140.899 
4163.404 
4185.909 
4208.4 4 
4230.919 
4253.424 
4275.929 
4298.434 
4320.939 
4343.44 1 
4365.949 
4388.454 
4410.959 
4433.464 
4455.969 
4478.474 
4500.979 


Value in 
Troy Ounces. 


8.486 

8 .533 

8.580 

8.627 

8.674 

8.721 

8.768 

8.814 

8.861 

8.908 

8 .955 

9.002 

9.049 

9.096 

9.143 

9.189 

9.236 

9.283 

9.330 

9.377 

















INDEX. 


A 

Aaron, references to, 155, 278, 
279, 281, 294,295, 296,307, 310, 
312, 315, 316, 34 6 > 38 i, 478. 

Aaron’s Assaying, 478. 

Acetate of Lead, re-agent, 154. 

Acetic Acid, re-agent, 158. 

Acicular Bismuth, mineral, 
466. 

Acid, Acetic, re-agent, 158. 

Acid, Citric, re agent, 160. 

Acid Fluxes, 239, 241; silica, 
142, 150. 

Acid Gangues, 239, 241. 

Acid, Hydrochloric (muriatic) 
re-agent, 161. 

Acid, Nitric, re-agent, 157, 162; 
preparation of various 
strengths, 225; to free from 
chlorine, 157. 

Acid, Sulphuric, re-agent, 165. 

Acid, Tartaric, 165. 

Actinium, element, 14. 

Aikinite, mineral, 441, 462, 466. 

Ainsworth balance, 57, 58. 

Alabandite, mineral, 245. 

Alaskaite, mineral, 462, 469. 

Alcohol, re-agent, 158. 

Algodonite, mineral, 441, 465, 
466. 


Alphabets and Figures, steel, 
137 - 

Altaite, mineral, 441,462, 465, 
469. 

Alumina, and lead phosphate, 
mineral, 471; crucibles, 109. 

Aluminium, element, 13. 

Amalgamation, assay, 365; 
mortar, 39. 

Amalgam, gold, mineral, 461. 

Am. Inst. Min. Eng., 348, 433. 

Ammonia, aqua (caustic, hy¬ 
drate, water), 158; carbonate, 
142, 148, 159; citrate, 160. 

Analysis, books 00,473; blow¬ 
pipe, books on, 475; copper 
ores, 347; definition, 15; re¬ 
agents for, 158; volumetric, 
books on, 474. 

Anatase, mineral, 441. 

Anderson’s Prospector’s 
Handbook, 436, 439. 

Anglesite, mineral, 337, 469. 

Annealing Cups, 117; plate, 

JI 7 - 

Antimonial ores, 202, 233; red 
silver ore, 182, 445,464; silver, 
463; sulphide of silver and 
lead, 463, 470. 

Antimony, and lead sulphide. 

5°5 




5°6 


INDEX. 


469; and silver sulphide, 182, 
464; arsenic and silver sul- j 
phide, 182,463; bismuth and 
lead sulphide, 470; copper and 
lead sulphide, 466, 469; cupel 
color, 206; element, 13; gray, 
246, 263; in copper ores, 363; 
metal, 16; native, 465; oxide, 
464; qualitative scheme for, 
254-5; sulphuret, 246; vapors, 
249. 

Anvils, and methods of mount¬ 
ing, 127. 

Apatite, mineral, 441. 

Apothecaries’ weights, tables 
of, 490. 

Apparatus, distilled water, 155; 
for analysis and assaying, 19; 
glass and porcelain, 118; grad¬ 
uated, 122; miscellaneous, 
124; sulphuretted hydrogen, 
164; used in furnace, 108. 

Appendix, 339. 

Aqua Ammonia, re-agent. 158. 

Argentiferous, gold, 461,463; 
grav copper, 183; lead ores, I 
183; ores, 182; pyrites, 184; 
zinc blende, 184. 

Argentic Nitrate, re-agent, 
162. 

Argentite, mineral, 246, 252, 
462. 

Argillaceous Schist, 441. 

Argol, re-agent, 141, 146, 236; 
reducing power, 175. 

“Arrastre,” Buck’s Labora¬ 
tory, 39. 


Arsenate, Lead, mineral, 470. 

Arsenic, antimony and silver 
sulphide, 182,463; cupel color, 
206; element, 13; in copper 
ores, 362, 364; native, 462,465; 
sulphuret, 246; vapors, 249. 

Arsenical, copper, 467; ores, 
202, 233; silver ore, 182, 463. 

Arsenide, Copper, mineral, 
466, 467, 469. 

Arsenopyrite, or arsenical 
iron pyrites, mineral, 1S1, 245, 
249, 252, 263, 441, 462, 465. 

Asbestos, mineral, 441. 

Ash, bone, 166. 

Assay, amalgamation, 365; base 
bullion, 418; certificate, 482; 
chlorination, 378; copper, 319; 
crucible, methods of, 278; 
galena, 326; gold and silver, 
184; gold and silver bullion, 
383; laboratory, plan of, 481; 
lead, 326; tin ores, 431; ton 
equivalents, 494; ton weights, 
and explanation, 66. 

Assaying, apparatus, 19; books 
on, 478; definition, 15; dry re¬ 
agents for, 141; free gold and 
silver ores, 343; methods of, 
194; of various minerals in an 
ore, 341; outfit, 483; re-agents 
used in, 141; wet re-agents 
used in, 155. 

“Astonishing,” 187. 

Atacamite, mineral, 466. 

Attwood, blow-pipe assaying, 
475; reference to, 13, 371. 







INDEX. 


507 


Aurichalcite, mineral, 466. 

Auriferous Sulphurets, 181, 

445 - 

Austin, I>. S., references to, 186, 
420. 

Average Samples, obtaining 
of, 33, 36, 38, 186, 193 

Avoirdupois to trov weights, 
tables of, 413. 

Avoirdupois Weights, tables 
of, 489. 

Azure Copper Ore (azurite), 
mineral, 315, 319, 466. 

B 

Balances, Ainsworth, 57, 58, 
59; Becker, 44, 51, 52, 53, 58, 
59; for weighing gold and 
silver beads, 50; Oertling, 54, 
57, 58, 59; special directions 
for, 60; Troemner, 44, 45, 51, 

5 2 , 53 , 54 , 58 , 59 - 

Balling’s Works on Assaving, 

478 . 

Barium, chloride (muriate), re¬ 
agent, 160; element, 13. 

Barker’s Elementary Chem¬ 
istry, 472. 

Barnard’s Metric System, 

479 - 

Barniiardite, mineral,313,441, 
465, 466. 

Bartlett’s Minerals of New 
England, 439. 

Barytes, mineral, 441, 442. 


Base Bullion, assay, 418; sam¬ 
pling, 420. 

Basic Fluxes, 142, 148, 239, 241. 

Basic Gangles, 239, 241. 

Batea, 138, 371. 

Baths, sand, 130. 

Battersea, crucibles, 112; fur¬ 
naces, 89-90. 

Battery, Bunsen carbon, 352; 
gravity, 354. 

Beads, gold and silver, balance 
for weighing, 50; inquarting, 
197, 228; parting, 197, 224; 
weighing, 197, 223. 

Beakers, glass, 122. 

Beaufay Crucibles, iii. 

Becker’s balances, 44, 51, 52, 
53 , 58, 59 ; P ul P scales, 44. 

Beresite, mineral, 441. 

Beringer, C. and J. J., refer¬ 
ence to, 365. 

Beryl, mineral, 441. 

Bi-carbonate of Soda, re¬ 
agent, 141, 142, 236; proper¬ 
ties, 142. 

Bi-chromate of Potash, re¬ 
agent, 159, 236. 

Bismuth, acicular (cupreous), 
456; cupel color, 206; element, 
13; in copper ores, 363, 364; 
lead and antimony sulphide, 
470; metal, 16; native, 462, 
465; ores, 441; scorifier color, 
205; silver, 464, 471; silver 
and lead sulphide, 462, 464, 
469, 471; sulphuret, 246. 










5°8 


INDEX. 


Bismuthinite, mineral, 441, 
462. 

Bi-sulphuret, or bi-sulphide 
of iron, 297. 

Bi-tartrate of Potash, re¬ 
agent, 141, 146, 175. 

Black, flux substitute, 141, 146; 
copper or oxide of copper, 
2 47> 3 i 5 » 3 i 8 , 4 68 ? glazed pa¬ 
per, 125; oxide of manganese, 
re-agent, 159; oxide of man¬ 
ganese, mineral, 247; silver, 
464; tellurium, 461, 471. 

“Black Jack,” 245, 447. 

Black Lead Crucibles, 109. 

Blake’s Handbook of Colo¬ 
rado, 435. 

Blende, 181, 202, 245, 252, 263, 
441,442; argentiferous, 184. 

“ Blicking,” 219. 

“ Blossoming,” 221. 

Blotting Paper, 126. 

Blow-pipe, 132; analysis, books 
on, 475; outfit, 485. 

Blue carbonate of copper (blue 
malachite, mountain blue), 

3 i 5 » 3 i 9 » 4 66 - 4 6 7 - 

Blue Copper, mineial, 467. 

Blue Vitriol, mineral, 467. 

Bodemann & Kerl’s works on 
assaying, 478; reference to, 
324 - 

Boiling Flasks, 120. 

Bone-ash, 166. 

Books, note, 124; list of useful, 
472. 

Borax, 141, 144; glass, prepara¬ 


tion of, 145; re-agent, 141, 144, 
236. 

Bornite, mineral, 246, 252, 313, 

44 L 465* 4 66 - 

Boron, element, 13. 

Bosworth, crusher, 28; fur¬ 
nace, 89, 91. 

Bottle, wash, 119. 

Bottles, re-agent, 118; sample, 
118. 

Boulangerite, mineral, 441, 
465, 466. 

Bournonite, mineral, 313, 466, 
469. 

Bowie, A. J. Hydraulic Min¬ 
ing, 477 - 

Boxes, sample, 125, 186. 

Boyer, C., reference to, 6. 

Bridgman’s, Ore Mixer and 
Divider, 37; Ore Sampling 
Machines, 34. 

Brief Scheme, for silica, iron 
and manganese, 427. 

“Brightening,” 219. 

Brittle Silver Ore, mineral, 
182, 464. 

Brochantite, mineral, 466. 

Bromic Silver, (bromide of 
silver, bromyrite), 183, 462. 

Bromine, element, 13; re-agent, 

159 - 

Brookite, mineral, 441. 

Brown Hematites, 441. 

Brown’s Assay Furnace, 89, 
92. 

Brushes, 126. 

Brush’s Mineralogy, 475. 





INDEX. 


509 


Bucking Hammer, 30. 

Buck’s Amalgam Mortar, 39. 

Buffalo Dental Mfg. Co., 
72, 84. 

Bullion, base, assay of, 418; 
gold and silver, assay of, 383; 
punch, 138. 

Bunsen, battery, 352; burners, 
130. 

Burette, 122; stands, 139. 

c 

Cadmium, element, 13; cupel 
color, 206; scorifier color, 205. 

Caesium, element, 14. 

Cairns’ Quantitative Anal¬ 
ysis, 473. 

Calaverite, mineral, 461, 465; 

Calcite, mineral, 441. 

Calcium, chloride, 160; ele¬ 
ment, 13; hydroxide, 161. 

Calc-spar, mineral, 292. 

Calculations in scorification 
process, 197, 230. 

Caledonite, mineral, 467, 469. 

Callon’s Lectures on Min¬ 
ing, 475. 

Capsules, porcelain, 120. 

Carbon, element, 13. 

Carbonate, of ammonia, re¬ 
agent, 142, 148, 159; of copper, 
blue and green, minerals, 315, 
319, 466, 468; of lead, min¬ 
eral, 184, 326, 469; of lead, re¬ 
agent, 154; of potash, re¬ 
agent, 141, 143, 236; of sodi¬ 


um, re-agent, 159, 236; of zinc 
and copper, mineral, 466. 

“ Carbonate Ores,” 181, 201, 
446- 

Carbonates, tests for, 422. 

“ Carbons, Pepper,” 408. 

Carpenter’s Mining Code, 
480. 

Carrollite, mineral, 313, 467. 

Case, Glass, for pulp scale, 44. 

Casserole, 123. 

Cassiterite, 431. 

Caustic ammonia, 158; lunar, 
162; potash, 160; soda, 160. 

Cerargyrite, mineral, 463. 

Cerium element, 14. 

Certificate of Assay, form 
for, 482. 

Ceruse, re-agent, 154. 

Cerussite, mineral, 184, 326, 
44L 465* 4 6 9- 

ChalcAnthite, mineral, 467. 

Chalcocite, mineral, 246, 252, 
312, 319, 467. 

Chalcopyrite, mineral, 246, 

252, 3i3, 3*9> 44L 462* 4 6 5> 467- 

Chalk, dry, 166; wash, 166. 

Chamois Skin, 140. 

Chapman’s crucible flux, 293. 

Chapman’s Furnace Assay, 478. 

Chapman, references to, 7, 187, 
293- 

Charcoal, Wood, charge for 
testing, 176; properties of, 
148; re-agent, 148, 236; reduc¬ 
ing power, 147, 176. 

Charges, Aaron’s general, 294, 








INDEX. 


5 10 

295; Chapman’s, 293; crucible, 
for galena, 317; crucible for 
quartz, sand, or “ dry ores,” 
2 95> 2 9 6 ; f or argol, 175; for 
charcoal, 176; for chlorides, 
201; for copper mattes, 200; 
for copper oxides and carbon¬ 
ates, 321; for copper oxides, 
314; for cream of tartar, 175; 
for “dry ores,” 296; for gran¬ 
ulated lead, 172; for iron ox¬ 
ide, 311, 312; for iron pyrites, 
2 99> 303, 305, 306, 307; for lead 
carbonates, 335, 336; for lead 
in galena, 326, 329, 330, 331, 
333; for lead oxides, 335, 336; 
for litharge, 168; for native 
copper, 320; for nitre, 177; for 
ordinary scorifications, J99; 
for oxides of iron, 201; for 
sulphurets of copper, 314,322; 
for tellurides, 202; for tin 
ores, 432; Mitchell’s, for all 
gold and silver ores, 291; for 
testing ores, 256, 265; general, 
for crucible, 290; in scorifi- 
cation process, 199; prelimin¬ 
ary, to determine oxidizing 
power, 265; preliminary, to 
determine reducing power, 
256; preparation of, in scori- 
fication process, 197; scorifi- 
cation for antimonial and 
arsenical ores, 202 ; for blende, 
202; for “ carbonate ores,” 
201; for “ chloride ores,” 201; I 
for copper glance or pyrites, | 


199; for copper matte, 200; for 
“every day” ores, 199; for 
galena, 201; for gray copper 
ore, 200; for native gold or 
silver, 203; for oxide of iron, 
201; for sulphurets of iron, 
200; for tellurides, 202; spec¬ 
ial, 296; Stone’s, 292. 

“ Checking,” i 16. 

“ Checks,” 404. 

Chemical Technology, Wag¬ 
ner’s, 472. 

Chemistry, Barker’s, 472; gen¬ 
eral, books on, 472; Miller’s, 
472; reference books on, 472; 
Roscoe and Schorlemmer’s, 
472; Roscoe’s Elementary, 
473; theoretical text-books on, 
472; Watt’s Dictionary, 472. 

Ciiem. News, references to, 365, 

433 - 

Chisel, cold, 138. 

Chloride, and phosphate of 
lead, 471; basic, 160; calcic, 
160; mercuric, 162; of silver, 
183, 463; sodic, 148; stannous, 
163. 

“ Chloride Ores,” 183, 201, 233. 

Chlorination assay of gold 
ores, 378; test for silver, 381. 

Chlorine, element, 13; in dis¬ 
tilled water, 156; to free 
nitric acid from, 157. 

Chlorite, mineral, 441. 

Chloritic-schist, 441. 

Chloro-arseniate of Lead, 

44 1 - 





INDEX. 


5 11 


Chloro-bromide of Silver, 

233 , 463 - 

Chromate of Copper and 
Lead, mineral, 469,471. 

Chrome iron, mineral, 441. 

Chromium, element, 13; colors 
in cupel and scorifier, 206. 

Chrysocolla, mineral, 240,316, 

44 L 4 6 7 - 

“ Churning,” 226. 

Citrate of Ammonium, re¬ 
agent, 160. 

Citric Acid, re-agent, 160. 

Classen’s Quantitative An¬ 
alysis. 473. 

Classification, of fluxes, 242; 
ofgangues, 241; of ores, 450-1; 
of ores in assaying, 233, 237; 
of silver ores, 182-4. 

Clay, crucibles, no; crucibles, 
French, 109, in; lute, 166. 

Clock-glasses, 119. 

Cloth, oil and rubber, 125. 

Coal, reducing power of, 147,176. 

Coates, R. G., references to, 6, 
378 . 

Cobalt, colors in cupel and 
scorifier, 207; element, 13; in 
copper ores, 361; metal, 16; 
nickel and copper sulphide, 
467 - 

Coffee-mill, 146. 

Coke, reducing power of, 147, 
176. 

Cold Chisel, 138. 

Collins’ Mining and Quarry¬ 
ing, 436, 477. 


Colorado crucibles, 112; min¬ 
erals, 471. 

Color ado it e, mineral, 462, 465. 

Color Tests, cupel and scori¬ 
fier, 204. 

“ Colors,” 365 

Columbium, element, 14. 

Common Salt, re-agent, 142, 
148. 

“ Concentrates,” 299. 

Copper, analysis, methods, 347; 
and antimony, 246; and iron 
sulphide, sulphuret or pyrites, 

246, 3 i 3 , 3 i 9 * 466. 467; and 
lead chromate, 469, 471; and 
si'ver sulphide or sulphuret, 
183, 464, 468; and uranium 
phosphate, 468; and zinc car¬ 
bonate, 466; argentiferous 
gray, 183; arsenical, 467; 
arsenide, 466, 467, 469; assay, 
319; azure, 466; black oxide, 

247, 3i5> 3i8, 468; blue, 467; 
blue carbonate, 315, 319, 466; 
blue malachite, 466; carbon¬ 
ates, 315, 319; cobalt and 
nickel sulphide, 467; colors in 
cupel and scorifier, 204; ele¬ 
ment, 13; glance, 199, 246, 263, 
312, 467; gray, 181, 200, 246, 
263, 3i3, 3 i 9 > 464. 468; green, 
468; green carbonate, 315, 319, 
468; indigo, 467; lead and 
antimony sulphide, 466, 469; 
matte, 200; metal, 16; metal¬ 
lic, 162; metallurgy, 476; min¬ 
erals in the United States, 





5 1 2 


INDEX. 


466; muriate, 466; native, 31S, 
465, 468; native, assay, 320; 
occurrence, 318; ores, 441; 
oxides, 315, 318; oxides, assay, 
315, 321; oxychloride, 466; 
phosphate, 468; purple, 466; 
pyrites, 199, 246, 263, 313, 
-441, 467; pyritous, 467; red 
oxide, 318, 441, 467; silica, 
467; spatulas, 42; sulph-arsen- 
ite, 467, 468; sulphate, 466, 
467; sulphides or sulphur- 
ets, 246, 312, 319, 467; sul¬ 
phides, assay, 321; tests for, 
424; uranite, 468; variegated, 
246, 466; vitreous, 246, 312 
467; vitriol, 467; volumetric 
analysis, 357. 

Copperas, re-agent, 163. 

Copp’s Mining Code, 436, 479. 

Corbin, II. H., reference to, 191. 

“Cornets,” 408. 

Corn Starch, reducing power 
of, 147. 

“Cornucopias,” lead, 405. 

Cornwall’s Blow-pipe Anal¬ 
ysis, 475. 

Corrosive Sublimate, re¬ 
agent, 162. 

Corundum, mineral, 441. 

“ Coruscation,” 219. 

Counterpoising, 41 i. 

Cov ellite, mineral, 313, 467. 

Cream of Tartar, re-agent, 
141, 146, 236; reducing power, j 
^ 147 , 175 - 

Crucible, process, 185, 194, 231. 


Crucible Tongs, 98. 

Crucibles, alumina, 109; Bat¬ 
tersea, 112; black lead (graph¬ 
ite, or plumbago,) charcoal- 
lined, 109; clay, no; “Colo¬ 
rado,” 112; Denver Fire Clay 
Co.’s, in, 112; French clav 
or “Beaufay,” 109, hi; gold, 
109; “Gramme,” 112; Hessian, 
iron, magnesia, platinum, 109; 
porcelain, 109, 120; quick¬ 

lime, 109; round, in; sand, 
no; silver, no; triangular 
in. 

Crushers, Bos worth, 28; 
Gates, 26; Taylor, 24. 

Crystallography, definition, 
439 - 

Cupel, color tests, 204; moulds, 
132; rake, 104; shovel, 104; 
tongs, 102. 

Cu PELL AT ION, 197, 214. 

Cupels, directions for making, 
115- 

Cupreous, bismuth, 466; oxide, 
467; sulphato-carbonate of 
lead, 467, 469. 

Cupric Oxide, mineral, 468. 

Cuprite (or cuprous oxide), 
mineral, 315, 318, 441, 467. 

Cups, annealing, 117. 

Cyanide of Potash, proper¬ 
ties, 144; re-agent, 141, 143, 
160. 

Cyclopaedia, Johnson’s Uni¬ 
versal, 472. 

Cylinders, measuring, 122. 




INDEX. 


D 

Dana, Manual of Geology, 474; 
Manual of Mineralogy, 436, 
475 References 10,434,471; Sys¬ 
tem of Mineralogy, 471, 474; 
Text Book of Geology, 474. 

Dangler Laboratory Lamp, 
131 - 

Dark Red Silver Ore, 182,464. 

Davies, D. C., Treatise on Min¬ 
erals, 477. 

Davyum, element, 14. 

Deciienite, mineral, 469. 

Decipium, element, 14. 

“ Decomposed Iron Ore,” 247. 

Definitions, of acid and basic 
(luxes and gangues, 239, 240; 
of analysis and assaying, 15; 
of crystallography, lithology 
and mineralogy, 439; of oxi¬ 
dizing and reducing ores, 242, 
243 . 

Dendritic Silver, 463. 

Denver Fire Clay Co.’s cru¬ 
cibles, hi, 112. 

Descloizite, mineral, 469. 

Desulphurizing Action, of 

I 

bi-carbonate of soda, 142; of 
carbonate of ammonia, 148; 
of cyanide of potash, 144; of 
iron, 154; of litharge, 153. 

Determination of, moisture 
in an ore, 429; oxidizing power 
of nitre, 167, 176; of ores, 265; 
reducing powers of argol, 175; 
charcoal, 176; cream of tartar, 


5 1 3 

175; ores, 256; reducing 
agents, 167, 175; specific grav¬ 
ity of minerals, 459; sulphur- 
ets in an ore, 254; sulphur in 
pyrites, 430. 

Diamond, mineral, 441. 

D1 -chromate, Potassic, re¬ 
agent, 159. 

Dictionary of Chemistry, 
Watt’s, 472. 

Didymium, element, 14. 

Diorite, mineral, 441. 

Directions for, cupellation, 
214; filtering, 350; mak- 
*ing distilled water, 155-6; 
operating Dangler lamp, 131 ; 
operating Hoskins’ furnaces, 
87, 88; operating ore mixer, 
38; operating ore sampling 
machines, 36; sampling ores, 
186; setting up and testing 
pulp scales, 45; special, for 
bullion balances, 60. 

Dishes, evaporating, 121: roast¬ 
ing, 112. 

Distilled Water, apparatus 
for making, 155-6; chlorine 
in, 156; re-agent, 155. 

Dividers, 32. 

Domestic Water Still, 155-6. 

Domeykite, mineral, 467. 

Douglas & Prescott’s Qual¬ 
itative Analysis, 473. 

“ Dressing,” charges, 286. 

“ Driving,” 406. 

Dry Re-agents, list of, 141. 

Dyscrasite, mineral, 463. 












INDEX. 


5 T 4 


Egleston’s Weights, Meas¬ 
ures and Coins, 479, 493. 

Egleston’s Metallurgy, 477. 

Elderhorst’s Blow pipe An¬ 
alysis, 475. 

Electrum, mineral, 461, 463. 

Elements, lists of, 13, 14. 

Elements of Chemistry, Mil¬ 
ler’s, 472. ’ 

Eliot and Storer’s Qualita¬ 
tive Analysis. 473. 

Ellis, G. H., reference to, 7. 

Embolite, mineral, 463. 

Emerald, mineral, 441. 

Enargite, mineral, 441, 465, 
467. 

Engineering and Mining 
Journal, reference to, 186, 
364, 419. 

English and French 
Weights, equivalents, 493. 

Epsom Salts, re-agent, 163. 

Erbium, element, 14. 

Erubescite, mineral, 246, 313, 
466. 

Eustis, W. E. C., reference to, 

348 . 

Evaporating Dishes, 121. 

“Every-day,” ores, 199. 

Explanation of assay ton 

weights, 66. 


Fahlerz, 246, 313. 
Fahlore. silver, 183. 


“ Feathering,” 218, 421. 
Feldspar, mineral, 441. 
Ferric Sesquioxide, 166. 
Ferrocyanide. Potassic, re¬ 
agent, 160. 

F erro-tellurite, mineral,441, 
462, 465. 

Ferrous, sulphate, re-agent, 
163; sulphide, re-agent, 163. 
Fielding, F. E., references to, 

7 , 357 , 384. 

Figures, steel, 137, 

Filings, Iron, re-agent, 154. 
Filtering, directions for. 350. 
Filter, paper, 125; stands, 139. 
“ F INENESS,” 397 1 . 

Fire Clay, in clay lute, 166. 

“ Flashing,” 219. 

Flasks, litre, 122, 123; parting 
or boiling, 120. 

Fletcher’s gas furnaces, 74, 

278, 331 - 

Floors, Muffle, 109. 

Flour, re-agent, 14 1, 146, 176, 

236. 

Flour Gold, 181, 237,461. 
Fluorine, clement, 13. 

Fluor Spar, mineral, 292, 441. 
Fluxes, acid, 239, 242; basic, 
239, 242; bi carbonate of soda, 
141, 142; black flux substitute, 
141, 146; borax, 141, 144; car¬ 
bonate of potash, 141, 143; 

Chapman’s crucible, 293; cy¬ 
anide of potash, 141, 143; 

flour, 141, 146; glass, 150; 

litharge, 142, 152; metallic, 










INDEX. 


151, 1 53; neutral, 144; nitre, 
142, 148; sand, 150; scales for, 1 
43; silica, 142, 150; Stone’s 
universal, 292. 

Fluxing Pots, hi. 

Foil, lead, re-agent, 151; lead, 
silver in, 151, 167, 174; silver, 
re-agent, 154. 

Foliated Tellurium, mineral, 

4 6l , 47 1 - 

Form for Certificate of As¬ 
say, 482. 

Foye’s Mineral Tables, 475. 

Frazer’s Mineral Tables, 

475 - 

Free Gold, 1S1, 461; assay of, 
in ores, 343; in ores, to grind, 
191. 

Free Milling Ores, 450. 

Free Silver, 463; assay of, in 
ores, 343; in ores, to grind, 

191. 

“ F reezing,” 223. 

Freieslebenite, mineral, 463, 
47a 

French Clay Crucibles, 109, 

111. 

French, or Metric Weights, 
65; equivalents in English 
weights, 493; tables of, 491. 

Fresenius’ Qualitative and 
Quantitative Analysis, 
473; reference to, 428. 

Frying Pan, 131. 

Fuel, Percy’s Metallurgy of, 
476. 

“ Fulguration,” 219. 


5 1 5 

Funnels, glass, 123; separatory, 

123. 

Furnaces, 70; apparatus used 
in, 108; Battersea, 89,90; Bos- 
vvorth’s, 89, 91; Brown’s, 89, 
92; Fletcher’s, 72, 74, 75; gas, 
group of, 73; Hoskins’, 84; 
“ Monitor,” 76; permanent,96; 
portable, 89; tools for, 98; 
using gaseous fuel, 71, 72; 
using liquid fuel, 71, 83; using 
solid fuel, 72, 89. 

I 

G 

Gadolinium, element, 14. 

Galena, or Galenite, 181, 183, 
201, 246, 252, 263, 325, 441, 
447, 462, 465, 470; crucible 
charge for, 317; iron in assay 
of, i 54 » 327 , 329, 33 i; methods 
for, 326; scorification charge 
for, 201. 

Gallium, element, 14. 

Gangues, acid and basic, 239, 
241. 

Garnet, mineral, 441. 

Gas Furnaces, Fletcher’s, 74, 
75; “ Monitor,” 76. 

Gas, hydrogen sulphide, re¬ 
agent, 163. 

Gates Crusher, 26. 

Gauze, wire, 130. 

“Gem Plate,” 106. 

General chemistry, books on, 
472; charges for crucible pro¬ 
cess, 290; qualitatitive and 







INDEX. 


quantitative analysis, hooks 
on,473;science, books on, 472. 

Geocronite, mineral, 465, 470. 

Geology, books on, 474. 

Germanium, element, 14. 

Glance, copper, 199, 246, 263, 
312, 467; lead, 183; silver, 
182, 246, 462; silver-copper, 
1 &3, 464, 468. 

Glass, and porcelain apparatus, 
118; beakers, 122; borax, 141, 
144; borax, preparation, 145; 
case for pulp scales, 44; flasks, 
120, 123; funnels, 123; magni¬ 
fying, 135; mortars, 124; pip¬ 
ettes, 123; re-agent, 150; stir 
ring rods, 123; spatulas, 42. 

Glasses, watch or clock, 119. 

Glossaries of mining terms, 
436 . 

Glucinum, element, 14. 

Glycerine, for sulphuretted 
hydrogen water, 165. 

Gneiss, 441. 

Gold, amalgam, 461, 465; and 
lead telluride, 461; argentifer¬ 
ous, 461, 463; assaying of, 184; 
assaying of free, 343; bid lion 
assay, 383; chlorination assay, 
378; crucibles, 109; crucible 
process, 231; element, 13; 
flour, free, leaf, native, nug¬ 
get, wire, 181,461; in silver 
foil, 154; Lock’s work on, 
476; metal, 16; minerals in 
L^nited States, 461; minerals 
likely to carry, 462; multipli¬ 


cation table, 487; native, 461, 
465; native, assay, 203; occur¬ 
rence, 181; pan test or “pan¬ 
ning,” 369; residues, weigh¬ 
ing of, 197, 229; tables of val¬ 
ues of, 417, 488; telluride, 461, 
471; testing of silver foil for, 
154; washing pans, 138. 

“Gold Weights,” 70, 396. 

Gold and Silver, and lead 
telluride, 461, 470; assaying, 
181, 184; beads, balances for 
weighing, 50; beads, weigh¬ 
ing of, 197, 223; bullion, assay 
of, 383; calculations, 197, 230; 
crucible process, 23i;cupella- 
tion, 197, 214; inquartation, 
197, 228; metallurgy, books 
on, 475; multiplication table, 
487; occurrence, 181; ores and 
minerals, article on, 434; ores, 
charges for, 291-296; parting, 
197, 224; preparation of 

charge, 197; preparation of 
sample, 185; residue, weigh¬ 
ing. *97. 229;roasting, 197, 199, 
271, 273; scorification process, 
195; table of values, 417, 488; 
tellurides, 461, 463, 464. 

Graduated Apparatus, 122. 

Grain Weights, 70. 

“Gramme” Crucibles, 112. 

Gramme Weights, 65. 

Granulated Lead, prepara¬ 
tion, 151; re-agent, 142, 151; 
testing for silver, 151, 167, 
172. 











INDEX. 


Granite, 441. 

“ Granulation,” 395. 

Graphic tellurium, mineral, 
461, 464. 

Graphic Crucibles, 109. 

Gray, antimony, 246, 263; cop 
per, 181, 200, 246, 263,313, 464, 
468; copper, argentiferous, 

183. 

Green, carbonate of copper, 
315, 319, 468; copper ore, 468; 
lead ore, 470; malachite, 319, 
468; mountain, 467, 468; vit¬ 
riol, re-agent, 163. 

Grinder, 30. 

Grinding Plate, 29; Mr. S. A. 

Reed’s, 31. 

Gum Arabic, 147. 

Gummed Labels, 124. 

H 

Hammers, 127. 

Hand Rolling Mills, 134. 
Hand Scales, 49. 

Hanks, II. G., Report of State 
Mineralogist of Cal., 7, 475. 
Hard Coal, reducing power of, 
147. 

Harrisite, mineral, 313, 467. 
Hart, references to, 365, 428. ! 

Hart’s Volumetric Analy¬ 
sis, 474. 

Heavy Spar, mineral, 292, 

44 1 • 

Helium, element, 14. 

Hematite, re-agent, 166; min- 


5'7 

eral, 310, 441; red and brown, 

44 1 - 

Henryite, mineral, 462, 465, 
470. 

Hessian Crucibles, 109. 

IIessite, mineral, 462, 463, 465. 

Hoffmann, Prof. H. O., on 
assay of tin ores, 433. 

Holmium, element, 14. 

Horn, silver, mineral, 182,463; 
spatulas, 42 ; spoons, 42. 

Horn-blende, mineral, 441. 

Hornblendic-schist, 441. 

“ Horse-flesh ” ore, 246, 313, 
466. 

Hoskins’ Assay furnaces, 84 

Hydrate, amnionic, re-agent, 
158; potassic, re-agent, 160; 
sodic, re-agent, 160. 

Hydric Nitrate, re-agent, 157. 

Hydrochloric Acid, re-agent, 
161. 

Hydrogen, element, 13; sul¬ 
phide, 163; sulphide, prepara¬ 
tion of, 164. 

11 ydro-potassic-tartr ate, re¬ 
agent, 146. 

Hydro-sodic-carbonate, re¬ 
agent, 142. 

Hydroxide, Calcic, re-agent, 
161. 

Hyposulphite of Sodium, re¬ 
agent, 161. 

I 

Idunium, element, 14. 

Ilmenium, element, 14. 









5>8 


INDEX . 


Implements for Pulveriz¬ 
ing, Sampling, etc., 20. 

Importance of Average Sam¬ 
ples, 186. 

Important Silver Ores, 182. 

Indigo Copper, mineral, 467. 

Indium, element, 14. 

Ingot Moulds, 136. 

Inquartation, 197, 228. 

Introduction, 13. 

Iodic Silver (iodide of silver, 
iodvrite), 183, 463. 

Iodide of Potash, re-agent, 
161. 

Iodine, element, 13. 

Iridium, element, 13. 

Iridosmine, mineral, 441. 

Iron, and copper sulphide, sul- 
phuret or pyrites, 181, 199, 
246, 313, 466, 467; and silver 
sulphide, 464; brief scheme 
for, 427; chrome, mineral, 
441; colors in cupel and scor- 
ifier ? 205; crucibles, 109; de¬ 
sulphurizing action, 154; ele¬ 
ment, 13; filings, 154; in cop¬ 
per ores, 363, 364; metal, 16; 
metallic, 162; mortars, 20, 22; 
nails, 154; oxide, 1S1, 201; ox¬ 
ide, crucible charges for, 311, 
312; oxide, re-agent, 155; ox¬ 
ides, 441; pyrites, crucible 
charges for, 299, 303, 305, 306, 
3°7; pyrites, mineral, 245, 
263, 297, 441; pyrites, re¬ 
agent, 142, 155; red oxide, 166, 
247; retorts, 140; spatula, 42;! 


sulphate, 163; sulphide or sul- 
phuret, re-agent, 163; sulphur- 
ets, ores, 200, 245, 246, 297; 
tests for, 424; titaniferous, 
442; wire, 154. 

Italcolumite, mineral, 441. 

Ivory Spatulas, 42. 

J 

“Jack, Black,” 245, 447. 

Jackson, J. C., references to, 7, 
98. 

Jamesonite, mineral, 470. 

Johnson’s Universal Cyclo¬ 
pedia, 472 

Joseite, mineral, 441, 462, 465. 

Judson’s cupel tongs, 103; scor- 
ification tongs, 101. 

K 

Kerl’s Metallurgy, 476; 
Works on Assaying, 478. 

Kobellite, mineral, 470. 

Kunhardt’s Ore Dressing, 

477 - 

Kustel, references to, 182, 379, 
381,383; Roasting of Gold and 
Silver Ores, 7, 182, 476, 

Kyanite, mineral, 441. 

% 

L 

Labels, gummed, 124. 

Laboratory, arrastre, 39; 
lamp, Dangler, 131; manipu¬ 
lation, books on, 474; mill- 
run, 365; plan of assay, 481. 









INDEX. 


519 


Lamborn’s Metallurgy, 476. 

Lamps, 130; Dangler laboratory, 

131- 

Lanarkite, mineral, 470. 

Lanthanum, element, 14. 

Laundry Starch, 147. 

Lead, acetate, re-agent, 154; 
and alumina phosphate, 471; 
and antimony sulphide, 469; 
and copper chromate, 469, | 
471; and gold telluride, 461, 
471; and silver, antimonial 
sulphide of, 463, 470; and sil¬ 
ver, metallurgy, 476; and zinc 
vanadate, 469; argentiferous 
ores, 183; arsenate, 470; assay, 
326; bismuth and antimony 
sulphide, 470; bismuth and 
silver sulphide, 462, 469; car¬ 
bonate, mineral, 184, 326, 469; 
carbonate, re-agent, 154; car¬ 
bonates, assay, 334; chloro- 
arseniate of, mineral, 441; col¬ 
ors in cupel and scorifier, 205; 
copper and antimony sul¬ 
phide, 466, 469; “cornucop¬ 
ias,” 405; cupreous-sulphato- 
carbonate, 469; element, 13; 
foil, re-agent, 151; foil, silver 
in, 151, 167, 174; glance, 183; 
granulated, preparation, 151; 
granulated, re-agent, 142, 151 ; I 
granulated, silver in, 152, 167, 
172; in copper ores, 363, 364;; 
metal, 16; metallurgy, 476; 
minerals, 469; molybdate, 
471; native, 471; ore, green, 


470; ore, white, 326, 469; ore, 
yellow, 471; ores, 325; argen¬ 
tiferous, 183; ores, assay, 326; 
ores, occurrence, 325; oxides, 
assay, 334; phosphate of alum¬ 
ina and, 471; phosphate and 
chloride of, 471; pyrites, 246, 
316; red oxide, 247, 326, 470; 
removal from litharge, 152; 
sheet, 151, 167, 174; silver and 
bismuth sulphide, 462, 464, 
469, 471; silver and gold tell¬ 
uride, 461, 470; spar, 471; 
sugar of, 154; sulph-antimo- 
nite, 470; sulph-arseno*anti- 
monite,47o; sulphate,mineral, 
469; sulphato-carbonate, 467, 
470; sulphates, assay, 326; sul¬ 
phide, or sulplniret, assay, 326; 
sulphide, or sulphuret, min¬ 
eral, 183, 246, 316, 325, 470; 
sulphide, iron in assay of, 327, 
329,-331; telluride, 469, 470; 
test for, 425; tungstate, 471; 
vanadate, 469; vitriol, 469; 
white, re-agent, 154; yellow 
oxide, mineral,47o;yellow ox¬ 
ide, re-agent, 152. 

Leadhillite, mineral, 470. 

Leaf Gold, 181, 461; silver, 463. 

Le Conte’s Elements of Ge¬ 
ology, 474; reference to, 434, 

Leucopyrite, mineral, 441,465. 

Lieber’s Assayer’s Guide, 
478. 

Light Red Silver Ore, 182, 

4 6 3 - 









5 2 ° 


INDEX 


Lime, in copper ores, 363; sul¬ 
phate of, 468; water, re-agent, 
161. 

Limonite, mineral, 310. 

Lignite, mineral, 462, 465. 

Lists and References, 461. 

Lists, copper minerals, 466; dry 
re-agents for assaying, 141 ; 
elements, 13, 14; gold miner¬ 
als, 461; lead minerals, 469; 
minerals carrying gold, 462; 
minerals carrying silver, 465; 
re-agents for analysis, 158; 
silver minerals, 462; useful 
boo^s, 472; wet re-agents for 
assaying, 155. 

Litharge, properties, 153; re¬ 
agent, 142, 152, 236; to free 
from red oxide, 152; silver in, 
153, 167, 168. 

Lithium, element, 13. 

Lithology, definition of, 439. 

Litre Flasks, 122. 

Lock’s Work on Gold, 476. 

Low, A. H., references to, 6, 307. 

Luckow method of copper an¬ 
alysis, 347. 

Lunar Caustic, re-agent, 162. 

Lute, Clay, 166. 


Magnesia, crucibles, 109; in 
copper ores, 363. 

Magnesite, mineral, 441. 
Magnesium, element, 13; sul¬ 
phate, re-agent, 163. 


Magnet, 135. 

Magnetic Iron Pyrites, etc., 
2 ^ 5 . 297 - 

Magnetite, mineral, 441. 

Magnifying Glass, 135. 

Magnolite, mineral, 462, 465. 

Makin’s Manual of Metal¬ 
lurgy, 477. 

Malachite, 315, 441, 468; blue, 
466; green, 319, 468. 

Manganblende, 245, 252, 
263. 

Manganese, black or di-oxide, 
159, 247; brief scheme for, 
427; colors in cupel and scor- 
ifier, 206; element, 13; in cop¬ 
per ores, 362; oxides, 441; sul- 
phuret, 245; test for, 425. 

M anipulati o n, laboratory, 
books on, 474. 

Marcasite, mineral, 297. 

Massicot, mineral, 470. 

Matrasses, 121. 

Matte, copper, 200. 

Mattes, 289. 

Measuring Cylinders, 122. 

Melaconite, mineral, 247, 315, 
318, 441, 462, 465, 468 

Mercury, chloride, 162; ele¬ 
ment, 13; metallic, 162; native, 
465; re-agent, 162; sulphuret, 
mineral, 246; with gold, 461. 

Metallic, copper, iron, mer¬ 
cury, zinc, 162; scales, 191, 
343 - 

Metallurgy and M i n i n g, 
books on, 476. 








INDEX. 


5 2 1 


Methods, assay for copper ox¬ 
ides and carbonates, 321; as¬ 
say for copper sulphides, 321; 
assay for galena, 326; assay 
for iron pyrites, 298; assay for 
lead oxides and carbonates, 
334; assay for native copper, 
320; of assaying, 194; of cop¬ 
per analysis, 347; of crucible 
assays, 278; special, 341. 

Metric System, books on, 

479 - 

Metric Weights, 65; equiva¬ 
lents in English, 493; tables 
of, 491. 

Miargyrite, mineral, 182, 463. 

Mica Slates, 441. 

Mill, coffee, 146; run, labora¬ 
tory, 365. 

Miller’s Chemistry, 472. 

“Milling Test,” 458. 

Mills, hand rolling, 134. 

Mimetite, mineral, 441, 470. 

“Mineral,” 246. 

Mineralogy, books on, 474; 
definition of, 139. 

Minerals, assaying of, in an 
ore, 341; copper, 466; gold,! 
461; gold and silver, 434 ; lead, 
469; likely to carry gold, 462; 
likely to carry silver, 465;. 
silver, 462; specific gravity of, 


Miscellaneous, apparatus, 124; 
materials, 166. 

Mispickel, mineral, 245, 441. 

Mitchell, references to, 84,96, 
US, 152, iS 3 , 218, 291,324,405. 

Mitchell’s Manual of As¬ 
saying, 7, 479. 

Moisture in ores, determina¬ 
tion of, 429. 

Molybdate of Lead, mineral, 
471 - 

Molybdenite, mineral, 441. 

Molybdenum, element, 13. 

Monazite, mineral, 441. 

“Monitor,” gas furnace, 76. 

Morfit’s Chemical Manipu¬ 
lation, 474. 

Mortar, amalgamation, 39. 

Mortars and Pestles, glass, 
124; iron, 20, 22; porcelain, 
124; spring attachment for, 
21. 

Mosandrium, element, 15. 

Moulds, cupel, 132; ingot, 136; 
scorifier, scorification, or slag, 
105. 

Mountain, blue,466,467;green, 
467, 468. 

Muffle, floors, 109; hoe or 
rake, 104; scraper, 107; shovel, 
104, 107. 

Muffles, 108. 


459 - 

Miners’ gold washing pans, 


Muller, 30. 

Muller ite, mineral, 641, 465, 


138; horn, 139. • | 470. 

Mining Law, books on, 479. Multiplication Table For 
Minium, mineral, 247, 326,470. Gold and Silver, 487. 







5 22 


INDEX. 


Mundic, 245, 297. 

Muriate, of baryta, re-agent, 
160; of copper, 466; of silver, 
4 6 3 - 

Muriatic Acid, re-agent, 161. 

N 

Nagyagite, mineral, 461, 465, 
471 - 

Nails, iron, re-agent, 154. 

Native, antimony, 441, 465; ar¬ 
senic, 441, 462, 465; bismuth, 
441, 462, 465; copper, 318, 441, 
465, 468; copper, assay, 320;; 
gold, 461, 465; gold,assay, 203; 
lead, 471; mercury, 441,465; 
palladium, 441; platinum, 441; 
silver, 462, 463; silver assay, 
203; tellurium, 441,462, 465. 

Needle Ore, mineral, 466. 

Neptunium, element, 15. 

Nickel, cobalt, and copper, sul¬ 
phide, 467; cupel color, 207; 
element, 13; in copper ores, 
361; metal, 16; scorifier color, 
266. 

Nitrate of Silver (or Argen¬ 
tic), re agent, 157, 162. 

Nitre, oxidizing power, 148, 
167, 176; re-agent, 142, 148, 
236. 

Nitric Acid, preparation of 
various strengths, 225; re¬ 
agent, 157, 162; to free from , 
chlorine, 157. 

Nitrogen, element, 13. 


Nixon, M. G., Amalgamation 
Assay, 365; reference to, 6. 
North’s Practical Assaying, 

479 - 

Norwegium, element, 14. 

Note Books, 124. 

Notes on Setting Up the 
Oertling Balance, 54. 

Nugget Gold, 181,461. 

o 

Ochre, plumbic, mineral, 470. 
Occurrence of Ores, copper, 
3i8;gold, 181; gold and silver, 
181; lead, 325; silver, 181. 
Oertling’s Balance, 54, 57, 
58, 59; notes on setting up, 

54 - 

Oil Cloth, for sampling, 125, 
Oil of Vitriol, re-agent, 165. 
Oldberg O., Weights, Meas¬ 
ures and Specific Gravity, 479. 
Order of Work, in assaying, 
185; in scorification process, 
197 - 

“ Ordinary Ores,” 295, 296. 
Ore, antimonial silver, 182; 
argentiferous gray copper, 
183; arsenical silver, 182, 463; 
assaying of minerals in, 341; 
azure copper, 466; brittle sil¬ 
ver, 182; dark red silver, 182, 
464; gray copper, 313, 464, 
468; green copper, 468; green 
lead, 470; “horse-flesh,” 246, 
313, 466; light red silver, 182, 













INDEX. 


5 2 3 


463; mixer and divider, 
Bridgman’s, 37; needle, 466; 
purple copper, 466; sampling 
machines, Bridgman’s, 34; 
“tile,”467; variegated copper, 
466; white lead, 326, 469; yel¬ 
low lead, 471. 

Ores, analysis of copper, 347; 
argentiferous lead, 183; arsen¬ 
ical and antimonial, 202; 
blende, 202; “carbonate,” 181, 
201; “chloride,” 183, 201; 

chlorination assay of gold, 
378; classification of, 450-1; 
containing free gold or silver, 
assaying of, 343; copper, 318, 
441, 466; copper, assay, 319; 
copper glance, or pyrites, 199, 
312, 441; copper matte, 200; 
copper, occurrence, 318; de¬ 
termination of moisture in, 
429; directions for sampling, 
33, 36, 38, 188; “every day,” 
200; free milling, 450; galena, 
201; gold, 181; gold, assay, 
184; gold, occurrence, 181; 
gold and silver, 181, 434; gold 
and silver, assay, 184; gold 
and silver, charges for, 291, 
296; gold and silver, occur¬ 
rence, 181; gray copper ore, 
200; important silver, 182; 
lead, 325; lead, assay, 3 2 6; 
lead, occurrence, 325; native 
gold and silver, 203; oxide of 
iron, 20] ; oxidizing powers, 
242; pulverizing, 190; reduc¬ 


ing powers of, 242; silver, 462 ; 
silver, assay, 184; silver, oc¬ 
currence, 181; smelting, 451; 
sulphurets of iron, 200; tellur- 
ides, 202; tin, assay, 431 ; vol¬ 
umetric analysis of copper, 
357 - 

Orton’s Undergrou n i> 
Treasures, 439. 

Osmium, element, 14. 

Outfit, assaying, 483; blow¬ 
pipe, 485. 

Overman’s Assaying, 479. 

Oxide, antimony, 464; copper, 
318; copper, black, 247, 315, 
318, 468; copper, red, 315, 
31S, 441, 467; cupric, 468; cup¬ 
rous, 467; iron, 181, 201; iron, 
crucible charges for, 311, 312; 
iron, re-agent, 155; iron, red, 
166, 247; lead, red, mineral, 
247, 326, 470; lead, red, to re¬ 
move from litharge, 152; lead, 
yellow, mineral, 470; lead, 
yellow re-agent, 152; manga¬ 
nese, black, mineral, 247; 
manganese, black, re-agent, 
159; uranium, 468. 

Oxides, copper,assay, 321; lead, 
assay, 334; manganese, 441. 

Oxidizing, action of bi-carbon¬ 
ate of soda, 142; action of 
nitre, 148; action of ores, 242; 
power of nitre, 167, 176. 

Oxy - Chloride of Copper, 
466. 

Oxygen, element, 13. 










5 2 4 


INDEX . 


P 

Palladium, element, 13. 

Pan Test or “ panning” for 
gold, 369. 

Pans, frying, 131; miners’ gold 
washing, 138; zinc sifting, 41. 

Papers, black glazed, blotting, 
brown or manila, filter, 
tissue, 125. 

“ Parting,” 197, 224. 

Parting Flasks, 120 

“ Pepper-carbons,” 408. 

Percy’s Metallurgy, 476. 

Permanent Furnaces, 96. 

Petzite, mineral, 461, 463, 465. 

Philippium, element, 15 

Phillips’ Assay f.rs’ Compan- ; 
ION, 436, 479. 

Phillips’ Metallurgy, etc., 

477 - 

Phosphate, and chloride of 
lead, 471; of alumina and 
lead, 471; of copper, 468; of 
uranium and copper, 468. 

Phosphorus, element, 14. 

Pincers, 126. 

Pipettes, 123. 

Plan of Assay Laboratory, 
481. 

Plate, annealing, 117; gem, 
106; pouring, 105; pulverizing 
or rubbing, 29. 

Platinum, crucibles, 109; dish, 
351 ; element, 14; metal, 16; 
spatulas, 42; vessels, 140, 
35 1 - 


Plattner, references to,97,485. 

Plattner’s Blow-pipe Anal* 

YSIS, 475. 

Plumbago crucibles, 109. 

Plumbic, acetate, re-agent, 154; 
carbonate, re-agent, 154; mon¬ 
oxide, re agent, 152; ochre, 
470. 

Plumbogummite, mineral, 471. 
Plympton s Blow-pipe De¬ 
termination, 475. 

| “ Points,” 410. 

Pokers, 107. 

Polybasite, mineral, 182, 463. 

Pomeroy’s Mining Manual, 
435 - 436 , 477 - 

Porcelain, and glass appara¬ 
tus, 118; casserole, 123; cruci¬ 
bles or capsules, 109, 12c; 
mortars, 124; spatulas, 42. 

Porphyry, 441. 

Portable Furnaces, 89. 

Potash, bi-carbonate, 236; car¬ 
bonate, 141, 143, 236; caustic, 
160; cyanide, 141, 143, 160; bi- 
or di-chromate, 159; bi-tar¬ 
trate, 141, 146, 175; ferrocyan¬ 
kle, 160; iodide, 161; nitrate, 
148, 167, 176; sulpho-cvanide, 
163; yellow prussiate, 161. 

Potassium, element, 14. 

Pots, Fluxing, hi. 

Pouring Plates, 105. 

Prefaces, 5. 

Preliminary Charges, to de¬ 
termine oxidizing power, 265; 
reducing power, 256. 











INDEX. 


Preparation of, borax glass, 
145; charge in crucible pro¬ 
cess, 281; charge in scorifica- 
tion process, 197; distilled wa¬ 
ter, 155; granulated lead, 151 ; 
samples, 185; various strengths 
of nitric acid, 225. 

Process, crucible, 185, 194, 195, 
231; scorification, 185,194, 195. 

Proof Centres, 402. 

Prospecting, 435. 

Proto-chloride of Tin, re¬ 
agent, 163. 

Proustite, mineral, 463. 

Prussiate of Potash, 161. 

Pseudomalachite, m i n e r a 1 , 
468. 

Pulps, scales for, 43; setting up 
and testing, directions for, 45. 

Pulverizer, 30. 

Pulverizing of Ores, 190; 
sampling, etc., implements 
for, 20; plate and rubbers, 29; 
manner of using, 192. 

Punch, bullion, 138. 

Purple Copper Ore, 313, 466. 

Pyrargyrite, mineral, 464. 

Py'rite, mineral, 245, 297, 441, 
462, 465. 

Pyrites, 245, 252, 263, 297, 441; 
argentiferous, 184; arsenical 
iron, 245, 249; copper, 199, | 
263, 313, 44b 4 6 7 5 crucible 
charges for, 299, 303, 305, 306, 
307; determination of sul¬ 
phur in, 430; iron and copper, 
181,313; iron, re-agent, 155; 


525 

iron, mineral, 441; magnetic 
iron, 245; of lead, 246, 316. 

Pyrolusite, mineral, 247. 

Pyromorphite, mineral, 337, 
471. 

Pyrrhotine, mineral, 441. 

Pyrrhotite, mineral, 245, 252, 
297. 

Q 

Qualitative Analysis, Doug¬ 
las and Prescott’s, 473; Eliot 
and Storer’s, 473; Fresenius’, 
473; general, books on, 473, 

Qualitative Tests, 422; car¬ 
bonates, 422; copper, 424; iron, 
424; lead, 425 ; manganese,425; 
silver, 425; sulphates, 423; sul¬ 
phides, 423; tellurides, 423. 

Quantitative Analysis, 
Cairns’, 473; Classen’s, 473; 
Fresenius’, 473; general, books 
on, 473; Rammelsberg’s, 473; 
special, books on, 473; Wohl¬ 
er’s, 473. 

Quartz, 441. 

Quicklime Crucibles, 109. 

Quicksilver, 162. 

R 

Rake, cupel, 104. 

R ammelsbe r g’s Quantita¬ 
tive Analysis, 473. 

Randall’s Quartz Operat¬ 
or’s Hand Book, 477. 










526 


INDEX. 


Raymond, R. W., reference 
to, 436. 

Re-agents, dry, for assaying, 
141; for analysis, 158: bottles 
for, 118; in scorification pro¬ 
cess. 196; testing of, 167; wet, 
for assaying, 155. 

Realgar, mineral, 441, 465. 

Red Hematites, 441. 

Red Oxide of, copper, 315, 318, 
441, 467; iron, 166, 247, 311; 
lead, mineral, 247, 470; lead, 
removal of, from litharge, 152. 

Reducing Power of, argol, 
charcoal, coke, corn starch, 
cream of tartar, gum arabie, 
hard coal, laundry starch, 147; 
ores, 242,236; reducing agents, 
147, 167, 173; soft coal, wheat 
flour, white sugar, 147. 

Reed, S. A., references to, 6, 

3i, 37«- 

R EFERENCE BOOKS ON CHEMIS¬ 
TRY, 472. 

References and Lists, 461. 

Report on Colorado Min¬ 
erals, 471. 

Report, Fourth Annual, for 
California, 384. 

Residues, gold, weighing of, 
197, 229. 

Retorting in scorifiers, 368. 

Retorts, iron, 140. 

Rhodium, element, 14; mineral, 
44L 

Ricketts’ Notes on Assay- 

% 

ING, 479. 


Ring Stand, 129. 

Roasting, carbonate of am¬ 
monia used in, 148, 277; char¬ 
coal used in, 273; dishes, 112; 
of ores in crucible process, 
271, 273; of ores in scorifica¬ 
tion process, 197, 199; silica 
used in, 273. 

Rocker, 30. 

Rods, glass stirring, 123. 

Rolling Mills, hand, 134. 

Roscoe, and Sehorlemmer’s 
Chemistry, 472; Elementary 
Chemistry, 473. 

Ross, W. A., hooks on blow¬ 
pipe analysis, 476. 

Round Crucibles, hi. 

Rubber, iron, 30; sheet or 
cloth, 123. 

Rubbing Plate, 29. 

Rubidium, element, 14. 

Ruby, mineral, 441. 

Ruby Silver, mineral, 182,444, 
463, 464. 

Ruddle, 166. 

Running crucibles in fire, 287. 

Ruthenium, element, 14. 

Rutile, mineral, 441. 

Rutley, reference to, 434. 

R utley’s Study of Rocks, 474. 

s 

Salt, Common, re-agent, 142, 
148. 

Saltpetre, re-agent, 148. 

Salts, Epsom, re-agent, 163; 
tin, 163. 











INDEX. 


Samarium, element, 14. 

Sample, bottles, 118; boxes, 
125, 186; preparation of, 185; 
shovels, 32. 

Samplers, 32. 

Samples, to obtain average, 33, 
36, 38, 186, 193. 

Sampling, of a vein, 437; of 
base bullion, 420; implements 
for, 20; systematic, 193. 

Sand, baths, 130; crucibles, no; 
in accidents to muffles, 212 
re-agent, 150. 

Sapphire, mineral, 441. 

Scales, and balances, 42; hand 
49; pulps and fluxes, 43; set¬ 
ting up and testing pulp, di¬ 
rections for, 45. 

Scales, metallic, 191, 343. 

Scandium, element, 14. 

Schapbachite, mineral, 464, 

471. 

Scheelite, mineral, 441. 

Scheme for silica, iron and 
manganese, 427. 

Schirmerite, mineral, 464, 471. 

Schist, chloritic, 441; hornblen- 
dic, 441, talcose, 442. 

Science, General, books on, 

472. 

Scissors, 134, 

Scoops, 139. 

SCORIFICATION PROCESS, 185, 
194, 195; borax glass in, 196; 
buttons from, 210; calcula¬ 
tions, 197, 230; charges, 199; 
cupellation, 197, 214; granu- 


527 

lated lead in, 196; inquarta- 
tion, 197, 228; order of work, 
197; parting, 197, 224; prep¬ 
aration of charge, 197; re¬ 
agents used for, 196; roast¬ 
ing of ores in, 197, 199; scori- 
fication, 197, 208; scorifiers 
from, 212; silica in, 196, 200, 
201,213; slag from, 212; the¬ 
ory of, 196; weighing gold and 
silver bead, 197, 223; weigh 
ing gold residues, 197, 229. 
Scorifier, color tests, 204; 

moulds, 105; tongs, 100. 
Scorifiers, 113; “retorting” 
in, 368. 

Scraper, muffle, 107. 
Selenium, element, 14. 
Selenpaladate, mineral, 441. 
Separatory Funnel, 123. 
Serpentine, mineral, 441. 
Sesquioxide, Ferric, re-agent, 

166. 

Setting Up the Oertling bal¬ 
ance, notes on, 54. 

Shears, 134. 

Sheet, lead, re-agent, 142, 151; 
lead, testing for silver, 151, 

167, 174; rubber, for sampling, 
125. 

Shovels, cupel, 104; sample, 
3 2 - 

Siderite, mineral, 442. 

Sieves, 40. 

Sifting, of Ores, 190; pans, 41. 
Silica, acid flux, 150, 242; brief 
scheme for, 427; in scorifica- 










INDEX. 


528 

tion process, 196, 200,201, 213; 
re-agent, 142, 150, 242. 

Silicate of Copper, mineral, 
316, 467. 

Silicic Di oxide, re-agent, 150. 

Silicon, element, 14, 

Silver, and antimony sulphide, 
182, 463, 464; and copper sul¬ 
phide, 183, 464, 468; and gold, 
beads, weighing of, 197, 223; 
and gold, metallurgy, 476; and 
gold, multiplication table, 
487; and gold ores and min¬ 
erals, 434; and gold ores, as¬ 
saying, 184; and gold ores, 
charges, 290, 296; and gold 
telluride, 461, 463; and gold 
values, table of, 417, 488; and 
iron sulphide, 464; and lead, 
antimonial sulphide of, 463, 
470; and lead, metallurgy, 
476; antimonial, 463, 464; an¬ 
timony and arsenic sulphide, 

182, 463, 464; arsenical, 463; 
assay, 184; assaying of 
ores containing free, 343; 
bismuth, 464; bismuth and 
lead sulphide, 462, 464, 469, 
471; black, 464; brittle, 182, 
464; bromic or bromide of 

183, 462; bullion, assay of, 
383; chloride, 183,463; chlori¬ 
nation, test for, 381; chloro- 
bromide, 463; copper glance, 
183, 464, 468; crucible, no; 
dark red, 182, 464; dendritic, ( 
463; element, 14; fahlore, 183; 


foil, gold in, 154; foil, re¬ 
agent, 154; free, 463; glance, 
182, 246, 418; gold and lead 
telluride, 461, 470; horn, 182, 
463; in copper ores, 362, 364; 
in granulated lead, 152, 167, 
172; in lead foil, 151, 167, 174; 
in litharge, 153, 167, 168; iodic 
or iodide of, 183, 463; lead, 
463; lead and bismuth sul¬ 
phide, 462, 464; light red, 182, 
463; metal, 16; metallurgy, 
476; minerals carrying, 465; 
minerals in United States, 462; 
muriate, 463; native, 462, 463; 
native, assay, 203; nitrate, re¬ 
agent, 157, 162; ores, 182; ores, 
assaying, 184; ores, import¬ 
ant, 182; ores, occurrence, 
181; ruby, 182, 444, 463, 464; 
spatulas, 42; sulphide or sul- 
phuret, 182, 246, 462; telluric 
or telluride, 463; tests for, 425; 
testing of granulated lead for, 
172; testing of litharge for, 
168; testing of sheet lead for, 
174; vitreous, 462; wire, 463. 

Silversmith’s Hand-Book 
for Assayers, 479. 

Slag from scorification process, 
212; moulds, 105. 

Slates, mica, 441. 

Smaltite, mineral, 442, 465. 

Smelting Ores, 451. 

Smith, J. A., Report on Colo¬ 
rado Minerals, 471. 

Soda, bi-carbonate of, 141, 142, 








INDEX. 


529 


236; carbonate of, re-agent, 

159, 2 36; caustic or hydrate, 

160. 

Sodic, bi-borate, re-agent, 144; 
carbonate, 159, 236; chloride, 
148; hyposulphite or thiosul¬ 
phate, 161. 

Sodium, element, 14. 

Soft Coal, reducing power of, 
147 - 

Spar, calc, fluor, heavy, 292; 
yellow lead, 471. 

Spatulas, 41. 

Special, charges for crucible 
process, 296; directions for 
bullion balances, 60; methods, 
341; quantitative analysis, 
books on, 473. 

Specific Gravity of Miner¬ 
als, 459- 

Sphalerite, mineral, 245, 442, 
462, 465. 

Spinel, mineral, 442. 

“ Spitting,” 221. 

Spoons, Horn, 42. 

Spring attachment for mortars 
and pestles, 21. 

“ Sprouting,” 221. 

Stand, burette, 140; filter, 139; 
ring, 129. 

Stannous Chloride, re-agent, 
163. 

Starches, reducing powers of, 
147, 176. 

Steatite, mineral, 442. 

Steel, alphabets and figures, 
137; spatulas, 42. 


Stephanite, mineral, 182, 464. 
Sternbergite, mineral, 464. 
STETEFELDiTE,mineral,i 83 ,464. 
Stibnite, mineral, 246, 252,442. 
Stirring Rods, glass, 123; 
wire, 275. 

Stoltzite, mineral, 471. 
Stone’s universal flux, 292. 
Stoves, 130. 

Stromeyerite, mineral, 183, 
313, 464, 468. 

Strontium, element, 14. 
Sublimate, corrosive, re-agent, 
162. 

Substitute, black flux, 141,146. 
Sugar, of lead, re-agent, 154; 
white, 147, 176. 

SULPH-ANTIMONITE OF LEAD, 

mineral, 470. 

SuLPH-ARSENITE OF COPPER, 
mineral, 467, 468. 

SULPH-ARSENO-ANTIMONITE OF 

Lead, mineral, 470. 
Sulphates, copper, 466, 467; 
iron, re-agent, 163; lead, 469; 
lime, 468; magnesium, re¬ 
agent, 163; test for, 423. 

S U L P H A T O-C ARBONATE OF 

Lead, mineral, 467, 470. 
Sulphides or Sulphurets, 
actions of and upon, 263; an¬ 
timony, 246; auriferous, 181, 
445; bismuth, silver and lead, 
462, 464, 469, 471; cobalt, 

nickel, and copper, 467; cop¬ 
per, 246, 312, 319, 467; copper 
and iron, 181, 246, 313, 319, 









530 


INDEX. 


466, 467; copper and anti- 1 
monj, 246; copper, lead and 
antimony, 466, 469; determin¬ 
ation of in an ore, 254; fer¬ 
rous or iron, re-agent, 163; 
iron, 200, 245, 297; iron and 
arsenic, 245; iron and copper, 
181, 199, 246, 313, 319; lead, 
183, 246, 316, 325, 470; lead 
and antimony, 469; lead, bis¬ 
muth, and antimony, 470; 
manganese, 245; roasting of, 
252; silver, 182, 246,462; silver 
and antimony, 182, 463, 464; 
silver and copper, 183, 464, 
468; silver and iron, 464; sil¬ 
ver and lead, antimonial, 463, 
470; silver, antimony, and 
ar enic, 182, 463, 464; tests for, 
248, 249, 250, 423; zinc, 184, 
245- 

SULPHOCYANIDE OF POTASSI¬ 
UM, re-agent, 163. 

Sulphur, element, 14; determ¬ 
ination of, in pyrites, 430; re¬ 
agent, 142, 155, 236. 

Sulphuretted Hydrogen, 
preparation, 164. 

Sulphuric Acid, re-agent, 165. 

“ Surcharge,” 410. 

Sutton, references to, 365, 428, 
429 

Sutton’s Volumetric Anal¬ 
ysis, 474. 

“Sweet” Ores, 275. 

Sylvanite, mineral, 461, 464, 

4 6 5 - 


Systematic Sampling of ores, 
36, 38, 186, 193. 

T 

Tables, apothecaries’ weights, 
490; assay ton weights in 
grammes, grains, etc., 494; 
avoirdupois to troA - weights, 
413; avoirdupois weights, 489; 
equivalents of English and 
French weights, 493; French 
or Metric weights, 491; mul¬ 
tiplication for gold and sil¬ 
ver, 487; reducing powers of 
reducing agents, 147; sulphur- 
ets, 252, 263; troy, 415, 490; 
troy to avoirdupois weights, 
415; values of gold and silver, 
417, 488; weights, 489. 

Talc, mineral, 442. 

Talcose-schist, 442. 

Tantalum, element, 14. 

Tartar, cream of, re-agent, 141, 
146; reducing power, 147,175. 

Tartaric Acid, re agent, 165. 

Taylor Crusher, 24. 

Technology, Chemical, Wag¬ 
ner’s, 472. 

Technology Quarterly, ref¬ 
erence to, 433. 

Telluric Silver, mineral, 463. 

Tellurides, 461; try scorifica- 
tion process, 202; gold, 461; 
gold and lead, 461, 471; gold 
and silver, 461, 463, 464; gold, 
silver and lead, 461, 470; lead, 












469, 47°; silver, 461, 463; test 
for, 423. 

Tellurite, mineral, 442, 462, 
465 - 

Tellurium, black, 461, 471; col¬ 
ors in cupel and scorifier, 207; 
element, 14; foliated, 461,471; 
graphic, 461, 464; native, 462, 
465; ores, 181, 442; with gold, 
461; yellow, 461, 464, 

Tellurpyrite, mineral, 442, 
462, 465. 

Tennantite, mineral, 313, 468. 

Tenorite, mineral, 247,315,442. 

Terbium, element, 15. 

Testing of, distilled water for 
chlorine, 156; granulated lead 
for silver, 172; litharge for 
silver, 168; pulp scales, direc¬ 
tions for, 45; re-agents, 167; 
sheet lead for silver, 174; 
silver foil for gold, 154. 

Test, Milling, 458. 

Tests, chlorination for silver, 
381; cupel and scorifier color, 
204, 208; qualitative for car¬ 
bonates, copper, iron, lead, 
manganese, silver, sulphates, 
sulphides, tellurides, 422-427; 
for sulphurets, 248, 249, 250. 

Test Tubes, 120. 

Tetradymite, mineral, 442,462, 

4 6 5 - 

Tetrahedrite, mineral, 246, 
252, 30 , 3 i 9 . 442 , 462, 4 6 4 * 468. 

Text-books on theoretical 
chemistry, 472. 


Thallium, element, 14. 

Theory of, crucible process, 
233; scorification process, 196. 

Thiosulphate, Some, re-agent, 
161. 

Thorium, element, 14. 

Thulium, element, 15. 

“ Tile-ore,” 467. 

Tin, element, 14; metal, 16; 
ores, assay, 431; ores, charges, 
432; ores, preparation of sam¬ 
ple, 431. 

Tinstone, mineral, 442. 

Tissue Paper, 125. 

Titaniferous iron, mineral, 
442 - 

Titanium, element, 14. 

Tongs, crucible, 98; cupel, 102; 
scorifier, 100. 

Tools, Furnace, 98. 

Topaz, mineral, 442. 

Torbernite, mineral, 468. 

Torrey and Eaton, reference 
to, 364. 

Tourmaline, mineral, 442. 

Trap Rock, 442. 

Treatise on, Chemistry, Ros- 
coe and Schorlemmer’s, 472; 
Ore deposits, Cotta’s, 474. 

Triangle, Wire, 129. 

Triangular Crucibles, hi. 

Triple Sulphuret of Cop¬ 
per, Lead, and Antimony, 
466, 469. 

Triplett^s IIow to Assay, 479. 

TROEMNER’sbalances, 51, 52,53, 

54 - 5 s * 595 P ul P scales, 44, 45. 










53 2 


INDEX . 


Troy Weights, tables of, 415, 
490; to avoirdupois, 415. 

Tubes, Test, 120. 

Tungstate of Lead, mineral, 

471- 

Tungsten, element, 14. 

u 

United States, minerals 
found in; copper, 466; gold, 
461; lead, 469; silver, 462. 

Universal Flux, Stone’s, 292. 

Uranium, and copper, phos¬ 
phate, 468; colors in cupel and 
scorifier, 207; element, 14; 
oxide, 468. 

Uranochalcite, mineral, 468. 

Useful Books, list of, 472. 

V 

Values of Gold and Silver, 
table of, 488. 

Vanadate of Lead, 469; and 
zinc, 469. 

Vanadium, element, 14; color 
in scorifier, 205. 

Van Wagenen’s Hydraulic 
Mining, 477. 

Variegated Copper Ore, or 
pyrites, 246, 313, 466. 

Vauquelinite, mineral, 469, 

47 1 * 

“Vegetating,” 221. 

Vessels, Platinum, 140. 

Vitreous Copper, 246, 312, 
467; silver, 462. 


Vitriol, blue, 467; copper, 467; 
green, reagent, 163; lead, 469; 
oil of, re-agent, 165. 

Volumetric Analysis, of cop¬ 
per ore, 357; Hart’s, 474; Sut¬ 
ton’s, 474. 

Von Cotta, reference to, 434. 

Von Cotta’s Ore Deposits, 

47. 

W 

Wade’s Mining Law, 480. 

Wagner’s Chemical Tech¬ 
nology, 472. 

Wash-bottle, 119. 

Wash, Chalk, 166. 

Watch-glasses, 119. 

Water, ammonia, 158; distilled, 
apparatus, 155-6; distilled, 
chlorine in, 156; lime, 161; 
reagent, 155; sulphuretted 
hydrogen, 163. 

Watt’s Dictionary of Chem¬ 
istry, 472. 

Wehrlite, mineral, 442, 462, 

4 6 5- 

Weighing, gold and silver 
beads, 197, 223; gold and sil¬ 
ver beads, balances for, 50; 
gold residues, 197, 229. 

Weights, 65; and measures, 
Egleston’s and Oldberg’s, 479; 
apothecaries’ tables, 490; as¬ 
say ton, 66; assay ton, ex¬ 
planation of, 66; assay ton, in 
grammes, grains, etc., 494; 
avoirdupois, tables, 489; avoir- 






INDEX. 


533 


dupois to troy, 413; equiva¬ 
lents of French and English, 
493; French, metric or 
gramme, 65; French or metric 
tables, 491; “gold,” 70; grain, 
70; tables of, 490; troy tables, 
415; troy to avoirdupois, 415. 

Wet Re-agents for assaying, 
155 - 

Wheat Flour, 146; reducing 
power, 147. 

White Lead Ore, mineral, 326, 
469; re-agent, 154. 

White Sugar, reducing power, 
147, 176. 

Whitneyite, mineral, 469. 

Williams’ Chemical Manip¬ 
ulations, 474. 

Wilson’s Mining Laws, 435, 
480. 

Window Glass, as re-agent, 
150. 

Wire, gauze, 130; gold, 181, 
461; iron, re-agent, 154; silver, 
463; stirring, 275; triangle, 129. 

Wohler’s Mineral Analysis, 

473 - 

Wood Charcoal, properties, 
148; re agent, 142, 148; reduc¬ 
ing power, 147. 


Work, order of, in scorifica- 
tion process, 197. 

W ulfinite, mineral, 471. 

Y 

Yellow, lead ore or spar, 471; 
oxide of lead, mineral, 470; 
oxide of lead, re-agent, 152; 
prussiate of potash, re-agent, 
161; tellurium, 461, 464. 

Ytterbium, element, 14. 

Yttrium, element, 14. 

z 

Zinc, and copper carbonate, 
466; and lead vanadate, 469; 
blende, 442; blende, argentif¬ 
erous, 184, 245, 263; color on 
cupel, 206; color of vapors, 
249; element, 14; in battery, 
162; in copper ores, 361, 364; 
metal, 16; metallic, re-agent, 
162; qualitative scheme for, 
254-5; sifting pans, 41; sul¬ 
phide or sulphuret, 184, 245, 
246. 

Zirconium, element, l.. 

Zircons, mineral, 442. 













. 













Brown’s Portable Assay Furnace. 



1st. 

2d. 

3d. 


4th. 

5th, 

6th. 


ADVANTAGES OVER OTHER FURNACES: 

Simplicity. Having no complicated parts to get out of order. 
Usefulness. It can be used both for muffle work and for crucible 
operations. 

Capacity. There is no other furnace manufactured, of similar dimen¬ 
sions, which can accommodate so large muffles. Size of muffle, 
12 x 6 x 4 inches. 

Durability. Being made of heavy sheet-iron, it cannot be bioken y 
handling nor injured by heating. 

Light Weight. Boxed, this furnace weighs but 145 pounds, as against 
300 to 400 pounds of other furnaces. 

Cheapness. This furnace is from one-third to two-thirds cheapei 
than any other furnace that will do as good work. 

This furnace will be properly boxed for transportation, complete foi $20. 

MADE ONLY BY 


£. H. SARGENT & CO., 

Dealers in Assayers' Material, 125 State St., CHICAGO. 















































































































































































E. H. SARGENT 
& CO. 

125 State St, CHICAGO. 


Importers and Dealers 
in 


ASS A VERS' 

MA TERIALS, 

AND 

LABORA TORY 
SUPPLIES. 


WE ARE AGENTS FOR 

J. H. Munktel’s Swedish Filter Paper, 

The Denver Fire Clay Crucibles. Muffles 
and Sconfiers, 

E. Merck’s and Dr. Schuchardt’s Pure 
Chemicals, 

Troemner’s & Becker’s Accurate Balances, 
Denver Assay Furnaces, of Fire Clay, 
Bosworth’s, Taylor’s & Gates’ Ore Crushers. 
Bridgman’s Ore Samplers and Dividers. 


Catalogues furnished on request. 
Assayer’s outfits furnished promptly. 





WALTER LEE BROWN. 


GEORGE H. ELLIS. 


Brown & Ellis, 

Assayers and 

Analytical chemists 


Assays of Ores, Gold and Silver Bullion, etc. 
Analyses and Testing of Alloys, Waters, 
Liquors, Poisons, Fertilizers, Coals 
and Cokes, Paints, Oils, Fats, 
Greases, and all kinds of 
Commercial Products. 


OFFICE AND LABORATORY, 

602 Benson Avenue, EVANSTON, Cook Co., Ills. 

(30 minutes’ ride from Chicago.) 


Students taken for Instruction 

in Assaying and Chemistry. 


SEND FOR TERMS. 




THE 


BUFFALO 

Dental. Manufacturing. 

COMPANY 


AX70ULD inform Chemists, 
’ ’ Assayers and others inter¬ 
ested, that they are the exclusive 
manufacturers and owners of pat¬ 
ents in the United States of 


FLETCHER’S 

CELEBRATED 

GAS 

LABORATORY 

APPLIANCES 


and are prepared to construct spe¬ 
cial gas or gasoline heating or 
melting apparatus for laboratories 
or factories, from original draw¬ 
ings. in addition to their already 
extensive apparatus. 

Parties desiring special appara¬ 
tus will find it of advantage to cor¬ 
respond. 

Catalogues of Laboratory Ap¬ 
pliances sent on application. 



Buffalo Dental Manufacturing Co., 




5S7 & 5S9 Main Street, Cor. Chippewa, 

BUFFALO, N. Y. 





































































































































































































































x «2)en\>er flare Glav> 
Gompanv 


I M PORTERS 

AND 

DEALERS in 


1635 LARIMER ST., 

DENVER, COLO. 


Assayers and Chemists’ Supplies , 



MANUFACTURERS OF 




Our Goods are tor sale 
by all dealers in 
Assayers’ Supplies. • 


E. H. SARGENT &, CO. 

Sole Agents in CHICAGO, ILLINOIS. 




































































































Laboratory Lamp 

FOR 

CHEMISTS, ASSAYERS, 

Druggists, Jewelers, Glass Blowers, Etc. 


No Soot, no Smoke, no Odor. Easily Operated, Quick Worker, Cheapest to Use. 

ITS ADUflNTAGES. 

1. Perfect simplicity. 6. Intensity of heat; 3 to 6 times 

2. Cheapness of operation. that of a Bunsen Burner. 

3. Steadiness of flame. 7. It gives either the reducing or 

4. Entire freedom from odor. oxidizing flame. 

5. Portability. 8. It consumes all carbon. 

It gives a flame and heat of absolute purity, making it suitable for the most 
delicate chemical operations, where gas cannot be used. 

An Indispensable Article around the Laboratory. 

The National Vapor Stove and Mfg. Co., 

CLEVELAND, OHIO, 

Sole Manufacturers. 

E. H. SARGENT & CO., CHICAGO, AGENTS. 





























BRIDGMAN’S 

Ore^^mpwngDeyiges. 

See Pages 81 and 82 of This Book. 



SOLD BY 

E. H. SARGENT & CO., 

CHICAGO. 


ESTABLISHED 1842. 

First Premium at Franklin Institute , 1845. 

First Premium at Centennial International Exhibition , 1876. 

J. BISHOP & CO., 

Sugartown, Chester Co., Pa. 

Refiners and Melters of Platinum, 

MANUFACTURERS OF 

CRUCIBLES, EVAPORATING DISHES, IGNITION TUBES, 

AND 

All Articles Made from Platinum, used by 
Analytical Chemists. 

Old Platinum Bought and Taken in Exchange. Scrap Melted at 

the Shortest Notice. 

All articles sent by Adams Express, directed to J. Bishop & Co., 
Malvern Station, P. R. R., will meet with prompt attention. Circulars 
sent free on application. 































JOHN TftYLOR & CO. 

NOS. 61 & 63 FIRST STREET, 

SAN FRANCISCO, CAL. 


Importers, Manufacturers and Dealers in 

Assayers’ Materials, 

Mine and Mill Supplies, School 
and Philosophical Apparatus, 
Chemicals and Chemical 
Glassware, etc. 

- —Ag ents f or— - 

DENNISTON SILVER-PLATED COPPER AMALGAM PLATES, 
BECKER’S AND TROEMNER’S ASSAY AND CHEMICAL 
BALANCES, OERTLING’S ASSAY AND BULLION 
BALANCES, GERMANIA LITHARGE, LEAD, 

ETC. MERCK’S CHEMICALS. 


All Leading Chemicals (many of California production)— 

Borax, Cyanide of Potassium, Bluestone, 
Boneash, Bicarbonate of Soda, Acids, Sulphur, 
Hyposulphite of Soda, Quicksilver, etc. 

At the Lowest Market Rates. 


Our Illustrated catalogue and discount sheet, also “ Assayers’ Tables” mailed 

free on application. 

JOHN TftYLOR & CO. 

Nos. 6 1 & 63 First St., 


SAN FRANCISCO, CAL. 






Baker & Adamson, 


MAN UFA C TURING 
CHEMISTS . 

EASTON, PA 


MA NUFA C 7 USERS OF 

Chemically Pure Acid and Chemicals for the 
use of Assayers and Analytical Chemists. 


SPECIALTIES : 

Chem. Pure Muriatic, Nitric, and Sulphuric Acids. 

C. P. Ammonia, free from Aniline. 

Chem. Pure Hydrofluoric Acid, in our Patented Ceresine 

Bottles. 

Test Lead, Nitrate of Potash, Potassium Cyanide, 
Carbonate of Potash, etc., etc. 


WRITE FOR PRICE LIST. 


Our Chemicals are used in the U. S. Mints and by the Leading Chemists 
and Assayers, and for sale by chemical dealers 
throughout the country. 





H€NRY TROeMNeR, 

710 MARKET STREET, PHILADELPHIA. 



ANALYTICAL AND ASSAY 

E&lanee^ and We 



In use at all the United States Mints and Assay 

Offices. 


A Full Description Sent on Application. 


















































Fraser & Chalmers, 

(INCORPORATED.) 



MANUFACTURERS OF 

MINING MACHINERY, 
STEAM ENGINES, 
BOILERS, 

CABLE AND ELECTRIC 
RAILWAY MACHINERY, 

AND MACHINERY FOR THE SYSTEMATIC 

MILLING, SMELTING & CONCENTRATION OF ORES. 


GENERAL OFFICES: 


Fulton and Union Streets, 

CHICAGO._ 

WORKS: 

CHICACO, ILL., 

U. S. A. 


43 Threadneedle Street, 

LONDON, E.C., ENC. 

ERITH ON THAMES, 
ENGLAND 


BRANCH OFFICES: 


NEW YORK, Room 43, No. 2 Wall St. 
DENVER, COLO., 1316 Eighteenth St. 
Salt Lake City, Utah, 7 W. 2d South St. 
HELENA, MONTANA. 
JOHANNESBURG, Transvaal, S. Af. 


LIMA, PERU, South America. 
TOR 10 , JAPAN. 

SHANGHAI, CHINA. 
CHIHUAHUA, MEXICO. 
CITY OF MEXICO, Mexico. 
2 da de Plateros, No. 10. 


























THIS BOOK IS FOR SALE 

-) BY ALL (- 

Booksellers and Dealers in ftssauer’s flouaratus 

THROUGHOUT THE' WORLD, 

And will be mailed (postpaidJ on receipt of 

$2.50 

By the Publishers , 

E. H SARGENT & CO., 

125 State St., CHICAGO, ILL. 

Or by the Author, WALTER LEE BROWN. 

Box 96, Evanston, III. 


34 7 93 












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